This Parsha, which, like the entire Sefer, is referred to as "שמות," names, begins by presenting a list of the names of Yaakov's twelve sons, the Bnai Yisrael (שמות א':א'-ה'). Rav Yosef Karo, the author of the Shulchan Aruch, in his mystical commentary on the Torah entitled Maggid Meisharim (פרשת שמות מהדורא קמא, בד"ה אבל), speaks about the general significance of certain names, indicating what tendencies people will have if they are given those names, and then analyzes the name of each of Yaakov's twelve sons, explaining what the name represents. The Gemara in Berachos (דף ז:) indicates, based upon a variant reading of a Posuk in Tehillim (מ"ו:ט'), that a person's name can greatly affect his life, an idea also found in the Midrash Tanchuma in Parshas Haazinu (אות ז'), which states that because one's name can sometimes lead a person to be good or bad, one should, prior to naming one's child, carefully examine all potential names in order to be able to give him a name which will enable him to become a Tzaddik; the Midrash goes on (שם) to examine the names of each of the ten spies, the Meraglim, sent to Eretz Yisrael by Moshe (עיין במדבר י"ג:ד'-ט"ו), demonstrating that their very names hinted at the disaster which befell them. Similarly, the Sefer Chassidim (סימן רמ"ד) writes that one's name can lead him either to good or to bad, and he shows, citing Pesukim, how if people are given certain names, they will likely be successful, while if they are given other names, they will not be successful; a person should thus daven that his name should be given only to good people, and he himself should not give his child a name associated with unworthy people or people who experienced suffering and misfortune, because the name itself might lead to bad things for the child. This idea that one's name can ultimately influence events in one's life is also expressed by the Gemara in Bava Basra (דף קמ"ג:), as explained there by Tosafos (שם בד"ה שהיו).
The Baal HaTanya (לקוטי אמרים תניא, שער היחוד והאמונה פרק א') writes that the Hebrew name of every object in creation somehow defines that object and represents its source of life, and the same holds true for people; similarly, Rav Chaim Volozhiner, in his commentary on Pirkei Avos called Ruach Chaim (פרק א' משנה א' בד"ה משה), writes that the name represents the Nefesh, the soul of a person, connecting the person to his roots in Heaven. The Sefer Maavar Yabok (מאמר ג', שפתי רננות, פרק כ"ג) also discusses the significance of names and how they are used, and states as well that the essence of life and death sometimes depends on one's name, adding that this is why we don't use the names of wicked people. The Ohr HaChaim, commenting on a Posuk later in the Torah (דברים ל"א:א' בד"ה וילך), also states that the names of the Jewish people correspond to their Neshomos, their souls; the Shaloh too (הקדמה לספר שני לוחות הברית, בית אחרון בד"ה וזה) writes that a name can describe the very essence and root of something.
Based on this, it can be understood why the Gemara in Yoma (דף פ"ג:) teaches that one can learn a lot about a person's character from his name; the same idea is found in the Midrash in Bereishis Rabbah (פרשה מ"ב סימן ח') and in Rus Rabbah (פרשה ב' סימן ה') where the meanings of different names are analyzed and it is made clear that these names accurately described the character of those who had them. The Ramban (ספר האמונה והבטחון, פרק י"ט בד"ה לא תשא) writes in general that the name which something has hints at its nature; he connects this, as do other authorities cited above, to the Posuk which describes how Adam HaRishon named all the living creatures (בראשית ב':י"ט). This idea that a name can sometimes accurately describe a person's character is actually stated explicitly by the Posuk in Novi describing a man named Naval (נבל), a word which means "disgusting," and was an accurate description of him (שמואל א' כ"ה:כ"ה). According to the Ari Zal, as cited in the Sefer Taamei HaMinhagim (עניני מילה, בקונטרס אחרון לסעיף תתקכ"ט בד"ה וראיתי, ועיין עוד בחלק ליקוטים- ענינים שונים שם בהערה לסעיף קט"ז בד"ה וכמו), Hashem actually grants special insight to parents who are about to name their child which inspires them to select the appropriate name that will somehow hint at the child's destiny and carry with it a certain Kedushah. This idea is also implied by the aforementioned Tosafos in Bava Basra (םש). It should be pointed out, though, that a person's name does not always accurately reflect his or her character, as there are good people who have ugly names and vice versa, as documented in the Midrash Tanchuma on our Parsha (אות ב') and in Parshas Shelach (אות ו'), as well as in the Midrash in Bereishis Rabbah (סימן ד' פרשה ע"ה) and in Bemidbar Rabbah (פרשה ט"ז סימן ז').
In view of all of the above cited evidence about the importance of the name one is given, the Gemara earlier in Yoma (דף ל"ח:) interprets a Posuk in Mishlei (י':ז'), which states that the name of a wicked person shall rot, to mean, as explained by Rashi in Yoma (שם בד"ה דלא), that a person should not give his child the name of a wicked person. According to Tosafos (שם בד"ה דלא), Rabbeinu Tam corrected the version of the text of the Mishnah in Kesubos (דף ק"ד: ועיין שם בתוד"ה שני) and of the Gemara in Shabbos (דף י"ב: ועיין שם בתוד"ה שבנא) in order to make it clear that the individuals referred to in those passages did not in fact have the names of wicked people; a similar idea is found in Tosafos in Megillah דף י: בד"ה רבה(), as pointed out by Rabbi Akiva Eiger in his Gilyon HaShas in Yoma (שם בד"ה תוס') and in Kesubos (תוס' שם בד"ה) and in Shabbos (שם בד"ה תוס'). The Midrash in Bereishis Rabbah (פרשה מ"ט סימן א') compares the names of wicked people to utensils which rot with disuse; the Eitz Yosef (שם בד"ה לכלי) and the Matnos Kehunah (שם בד"ה הנחתם) explain that after the death of a wicked person, his name is forgotten because people don't use that name for other people. The Midrash (םש) then shows how the names of the Avos and the Shevatim continue to be used, as opposed to the names of wicked people. The Rashba writes in general (שו"ת הרשב"א חלק ד' סימן ל') that the giving of a name provides something with permanence and a lasting value, while that which has no permanent value really should have no name at all, including wicked people, and this implies hat the names of wicked people should therefore not be used; Rabbeinu Chananel in Yoma (שם בד"ה פי' שם) states that a person who is given the name of a wicked person will not have success in life. This ruling which prohibits the use of the name of a wicked person is cited by the Beis Shemuel in his commentary on the Shulchan Aruch אבן העזר סימן קכ"ט, שמות אנשים אות א'( בד"ה אבי שלום); the Maharsha in Taanis (בחדושי אגדות לדף כ"ח. שם בד"ה הוא) likewise seems to understand that this is a full-fledged prohibition, although other Acharonim are quoted in the Sefer Otzar HaBris (חלק א' פרק ו', קונטרס זה שמי לעולם, סימן ה' הערה א') as holding that it is proper as a מדת חסידות, an act of piety, to be careful to avoid the names of wicked people, but it is not an absolute prohibition to use these names.
The Ritva, commenting on this Gemara in Yoma (חידושי הריטב"א שם בד"ה דלא), asks why people use the name Yishmael (there was, for example, a famous Kohein Gadol and a Tanna named Rabbi Yishmael) when Avraham Avinu's son Yishmael was a wicked person, and he answers that some hold that Yishmael eventually did Teshuvah, an idea mentioned by the Gemara in Bava Basra (:דף ט"ז) and by Rashi in Chumash (עיין בראשית ט"ו: ט"ו בד"ה תקבר, ושם כ"ה:ט' בד"ה יצחק), and therefore his name may be used in subsequent generations. The Tosafos Yeshanim in Yoma (שם בד"ה דואג) seem ready to agree that if a wicked person does Teshuvah, his name may be used, but they point to a Gemara in Sanhedrin (דף ק"ד.) which implies that Yishmael did not actually do Teshuvah, and therefore suggest, as the Ritva (םש) does as well, that the name Yishmael may be used because it was Hashem Himself who selected that name (עיין בראשית ט"ז:י"א); according to the Yershalmi in Berachos (פרק א' הלכה ו', דף י"א:), though, this fact attests to the notion that Yishmael was in fact righteous at some point. In any event, it is clear that if a wicked person is known to have done Teshuvah, his name is acceptable for future usage.
The Ramo (שו"ת הרמ"א סימן מ"א) writes that one may use the name of a wicked person if there are other people besides that wicked person who have this name, and he asserts that this is also the position of the Tosafos in Kesubos (םש) and in Yoma (םש) cited above; it is noted in the Piskei HaTosafos in Sotah (אות כ') that this prohibition against using a wicked person's name applies only if the person is completely wicked. The Pnei Yehoshua, commenting on the aforementioned Tosafos in Kesubos (גזירות בד"ה תוספות שם בריש פרק שני דייני), suggests that the prohibition applies only if there is something about the name itself which indicates that the person with this name was wicked; he also suggests that there may be no prohibition if the name in question is not the wicked person's main name, a suggestion found as well in the Sdei Chemed (כללים, מערכת הרי"ש כלל מ"א). The Sdei Chemed (םש) also quotes a view that any name found in the Torah, even that of a wicked person, may be used. The Chida, in his Sefer Sheim HaGedolim (מערכת גדולים, ערך מר רב אברהם גאון), suggests that if the name itself is pleasant and good, one may use it without worrying that a wicked person had that same name. The Sefer Otzar HaBris cited above (שם סעיף א') quotes many of these sources, and also cites views that one may give his child the name of someone who became wicked only later on in life, as well as the name of a relative even though that person may have been wicked.
The Maharam Schick, who was an outstanding student of the Chasam Sofer, writes a lengthy Teshuvah (שו"ת מהר"ם שי"ק חלק יורה דעה סימן קס"ט) in which he forcefully asserts that it is forbidden for a Jew to use a secular or a gentile name, understanding that to do so violates the prohibition against imitating the ways of the non-Jews, a prohibition codified by the Rambam (פרק י"א מהל' עבודת כוכבים הלכה א') and the Shulchan Aruch (יו"ד סימן קע"ח סעיף א'); the Darkei Teshuvah (שם ס"ק י"ד) accepts this view of the Maharam Schick (םש) that using a non-Jewish name is a violation of Torah law, as is any imitation of non-Jewish behavior patterns, such as their style of dress. The Maharam Schick (םש) sharply attacks those who abandon their Jewish names in favor of non-Jewish ones, using their Jewish names only when called to the Torah for an Aliyah, and he documents sources which indicate that Jews always distinguished themselves through the use of their Jewish names, and were never embarrassed by them; he thus concludes that it is proper for a good Jew to use only his Jewish name. The Sefer Otzar HaBris (שם סימן ו' הערה א') quotes the famous story that the Maharam Schick was alive at the time when Jews were forced to adopt family names (surnames), and his father selected the name "Schick" because its Hebrew spelling, שיק, is an acronym for the phrase "שם ישראל קודש," which means "the Jewish name is holy," in order to stress the fact that he took on a name in addition to his Jewish name only because he absolutely had to.
The Rogatchover Gaon, however (שו"ת צפנת פענח סימן רע"ה), states that one is allowed, if necessary, to use a secular translation of one's Hebrew name. Rav Moshe Feinstein (העזר חלק ג' סימן ל"ה שו"ת אגרות משה אבן) writes that although it is indeed improper to use non-Jewish names, there is no real prohibition against doing so, and he adds that just as people speak languages other than Hebrew, they may use other names as well. Rav Feinstein elsewhere (שם אבן העזר חלק ד' סימן ק"ב) discusses which name, the Jewish or the secular, is the primary name, concluding that it is the former, but he clearly accepts the fact that Jewish people today do indeed use secular names. Interestingly, the Gemara in Gittin (דף י"א:) already states that most Jews living outside of Eretz Yisrael have non-Jewish names. In yet another Teshuvah (שם אורח חיים חלק ד' סימן ס"ו), Rav Feinstein cites many great authorities from the past who had non-Jewish names, explaining that once certain names become accepted and popular among the Jews, there is nothing wrong with them, even if originally there may have been some question about using them. Rav Feinstein (םש) does mention the famous idea found in the Midrash in VaYikra Rabbah (פרשה ל"ב סימן ה') and in many other places that one of the things which led to Bnai Yisrael's redemption from Mitzrayim was the fact that the people maintained their Jewish names (maintaining a style of dress, by the way, is not mentioned in those sources, as is commonly expressed), an idea stressed in the aforementioned Teshuvah of the Maharam Schick (םש). Rav Feinstein (םש) suggests, though, that perhaps this was critical only before the Torah was given, when there was little else to distinguish Jews from non-Jews, but after the giving of Torah, the Jews' role is simply to observe the Mitzvos commanded in the Torah, and therefore this idea about using only Jewish names may not be as critical. Nonetheless, there is certainly nothing wrong with using one's Jewish name, or with giving one's children only Jewish names, and this should perhaps be encouraged, especially in light of the views presented above which assign such great significance to one's name and its connection to one's Neshomoh.