In my other blog I wrote about when we name boys and girls, and why we name them at the bris and at a Torah reading, respectively.
Yossele Weisberg z"l, dedicated a chapter of his magnum opus on the laws and practices of the Bris Milah experience, "Otzar Habris," to the customs surrounding when we name both boys and girls. He records 4 reasons for why a boy is named at his bris:
- At the time we are involved in blessing the child (ie. we say a "mi sheberach" after the bris), it is appropriate to refer to him by name. This would imply that the bris is the latest we can name a boy.
- Until his bris, he carries the name of an "arel" ערל (uncircumcised), which must be changed to a proper Jewish name as soon as possible after his circumcision.
- When we give the name with the formula of "Kayem" קיים את הילד הזה לאביו ולאמו ויקרא שמו בישראל... (establish this baby to his mother and father with the following Jewish name…), we are asking for the name to carry with it "God's approval," which would surely be most forthcoming once the child is circumcised.
- Once he is circumcised, and has arrived at his personal physical "completion" (shlemut), it is the right time for him to be given his name.