"She conceived and bore a son, and he named him Er. She conceived again and bore a son, and named him Onan. Once again she bore a son, and named him Shelah; he was at Chezib when she bore him." RASHI interprets Chezib as the name of a place. Why does RASHI needs to inform us where it took place? In the book Da'at Zekeinim it says that the custom of old was as follows: The first son's name would be chosen by the father and the mother would name the second; once the father and once the mother and so on. Here, in the case of the first son, it is written "and he named him Er", in the masculine, meaning to say, Yehuda named him. In the second case the text says "and named him Onan", in the feminine form, meaning that his mother named him - in keeping with respectful practice and with their custom. But according to custom, it would have been appropriate that Yehuda be the one to name the third son. How is it that it was his mother who named him, as written in the text, "and named him Shelah"? This is what RASHI comes to explain. "He was in Chezib when she gave birth to him", meaning that Yehuda was not there at the time of Shelah's birth; Yehuda was in a place called Chezib, and therefore it was his mother who named him.