Moed Katan 15b: A mourner is forbidden to bathe, as it says, “Do not anoint with oil” (Shmuel II 14:2) – and bathing is included in anointing.

Yoreh Deah 381:1. Rema: By law, this is only forbidden during shiva, but the custom today is to forbid bathing for the whole shloshim. And we should not change this custom, since it is an old custom, established by great rabbis.

מועד קטן טו ע”ב: אבל אסור ברחיצה, דכתיב (שמואל ב׳ י״ד) ואל תסוכי שמן, ורחיצה בכלל סיכה.

יו”ד סימן שפא,א: רחיצה כיצד, אסור לרחוץ כל גופו אפילו בצונן, אבל פניו ידיו ורגליו בחמין אסור בצונן מותר, ואם היה מלוכלך בטיט וצואה רוחץ כדרכו ואינו חושש: הגה וכל זה מדינא אינו אסור רק שבעה אבל אח״כ מותר ברחיצה אלא שנהגו האידנא לאסור כל רחיצה כל ל׳ יום ואפי׳ לחוף הראש אסור ואין לשנות המנהג כי מנהג קדום הוא ונתייסד על פי ותיקין.

One day in 1876, a guest was sitting with R’ Yitzchok Elchonon Spector, when a man came in and asked, “Rabbi, I am a mourner. Am I permitted to go to the bathhouse?” Without hesitation, he answered him, “You are permitted.”

The questioner was not satisfied with this instant response, and spoke again: “Rabbi, I am in mourning for my father.” “Permitted, you are permitted,” the rav answered, using a double expression.

But this still did not settle the mind of the questioner, who asked a third time, “Only to sweat, or even to wash in hot water?” The rav answered him with a friendly smile, but also with surprise: “I just told you that you are permitted, and I said it without adding any details or qualifications. If so, go without delay, before I change my mind!”

After the man left, the rav looked at the guest, noticing his amazement, and guessing his thoughts. How and why could he rule leniently, contrary to the ruling of the Rema, who cites an enactment of the early rabbis? He said jokingly, “My guest will go on his way and tell people that the head of the Beis Din of Kovno gives hasty, mistaken rulings.” The guest also responded in jest, “Certainly I will.”

“If so,” said the rav, “let me ask you: do you know the Maharshal’s reason for forbidding bathing?” The guest answered: “Because of the prohibition against having a haircut; for the usual way is to have a haircut in the bathhouse.” “In that case,” continued R’ Yitzchok Elchonon, “why are we allowed to bathe during Chol Hamoed? That is also a period when we are forbidden to have a haircut! I know that this is the problem posed by the Taz on Yoreh Deah 381:1, and he answers that since everyone is forbidden to have a haircut then, we do not worry that one might forget.” He smiled, “Here too, today is one of the days of Sefiras Haomer, when the custom is to forbid haircuts. So why would this man forget and get a haircut? Therefore, he is allowed to bathe.

“I urged the questioner to go immediately, because it looked like he wanted to argue against my ruling. He wanted to object that the prohibition on haircuts during Chol Hamoed is a real Rabbinic prohibition, while during Sefirah it is only a minhag. I did not want to enter into a detailed discussion with him, so I did not point out to him that the prohibition against bathing in hot water after shivah is also only a minhag.”

Source: Mourning in Halacha, p. 211

[His last point is that the questioner could have objected that perhaps people will take the minhag of Sefirah lightly and get haircuts in the bathhouse during Sefirah. R’ Yitzchok Elchonon’s response is that the minhag not to bathe during shloshim was not set up for such people who take minhagim lightly, because then why would they respect this minhag in the first place? Rather the “minhag vasikin” brought by the Rema was aimed at carefully observant Jews, and such people would never come to take a haircut in Sefirah.]

Moed Katan 25b: Rabbi Chanin, son-in-law of the Nasi, had no children. He prayed for children and got one, but on the day his son was born, he died. The eulogizer said, “Happiness was turned into sorrow, rejoicing and sadness joined together. At the time of his joy he sighed, at the time that he was graced, his grace went lost. They named him Chanin after him.

מועד קטן כה ע”ב: רבי חנין חתניה דבי נשיאה הוה, לא קא הוו ליה בני, בעא רחמי והוו ליה. ההוא יומא דהוה ליה ־ נח נפשיה. פתח עליה ההוא ספדנא: שמחה לתוגה נהפכה, ששון ויגון נדבקו, בעת שמחתו נאנח, בעת חנינתו אבד חנינו. אסיקו ליה חנן על שמיה.

On 28 Sivan 5701 (June 23, 1941) the German army marched into Lithuania, murdering most of the Jews in its path and herding the rest into ghettos. Among those in the Kovna ghetto was the Lieberman family. The husband had gone to Vilna for a few days, leaving his pregnant wife and young daughter at home, when the Germans attacked. From then on, all communication was cut off between Vilna and Kovna, and Mrs. Lieberman had no idea whether her husband had survived or not.

One day, however, a friend of her husband came from Vilna and said that he and several hundred other Jews, including her husband, had tried to escape from Vilna on foot. In the middle of the road from Vilna to Kovna, German airplanes flew over them and rained down upon them deadly fire, killing many of them. From then on he did not see her husband, and so he assumed he was among the dead. Hearing this, the young wife cried uncontrollably over her husband. Left alone in the world with a young orphan daughter and a baby soon to be born, she would not be consoled and declared that she would go to her grave mourning for her husband.

With Hashem’s kindness, she was able to survive the war hiding out among the gentiles. After the liberation, to her shock, her husband came back from the plains of Russia, where he had fled and survived. The couple’s happiness was boundless. But then the husband noticed his wife calling their young boy by his name. “I named him in memory of you, thinking that you had died,” she explained. He refused to accept this. “One cannot name after a living person. We must change the boy’s name, and even his official documents, so that no one ever calls him by my name again.” The couple came to Rabbi Ephraim Oshry, posek of the Kovna ghetto, to ask what they should do. 

He began by proving that in the time of Chazal, they did indeed name children after living people. When Rabbi Nosson advised a mother on how to do bris milah safely, she named the baby Nosson (Shabbos 134a). When Rabbi Elazar son of Rabbi Shimon paskened that 60 women were ritually clean, they named their babies Elazar (Bava Metzia 84b).

That is when they named after a gadol hador. As far as naming after an ancestor, we find the Tanna Rabbi Prata son of R’ Eliezer, son of R’ Prata the Great (Gittin 33b). Either the grandfather was already deceased and we would say that they only named after dead ancestors, not live ones; or the grandfather was still alive and we would see from here that although they named after live ancestors, they did not name after fathers, only grandfathers.

[Similarly, we find that the line of Hillel’s dynasty was Hillel, Shimon, Gamliel (Hazakein), Shimon, Gamliel (of Yavneh), Shimon, Rebbi Yehuda Hanasi. If the grandfathers were alive, we would see from here than they named after the living, but not a father.]

The Sephardim carried on this custom, but the Ashkenazim today name only after the dead. If an Ashkenazi were to name after a living grandfather, we would leave the name, since he followed a valid custom. But naming a son after a father was never done in any Jewish community. The only time we find this in Chazal was in the case of a father who died just as his son was born: Rabbi Chanin (Moed Katan 25b).

As to the reason why sons were never named after fathers, Rabbi Oshry proposes that when the father calls his son, he would look crazy in the eyes of others. Also, among Ashkenazim, the father would feel that a son named after him was a bad sign for him.

Furthermore, R’ Yehuda Hachasid wrote in his Tzavaah that one should not marry a girl whose father has the same name as him, or a girl whose name is the same as his mother’s. Presumably the reason for this is that if the young couple lives with their parents, one would not be able to call the other by name (as the Rambam says in Mamrim 6:3). If the son and the father had the same name, it would similarly lead to disrespect for the father when other members of the family call the child.

Therefore, Rabbi Oshry ruled that the name of the boy should be changed, both in everyday life and on official documents.

Source: Shailos Uteshuvos Mimaamakim v. 5 Siman 13