Circumcision

[Wyrd of Gawd]

That convo is a short one, about a small subset of circumcisees (lol).  It's entirely common for a tribe to practice a form of ritual mutilation.  It likely developed from a consensual rite of passage, but by the time we have any written indication of the practice in jewish culture it had already been mythologized.  The purpose, however, remained clear; it was an announcement that the boy belonged to the tribe, and that any boy who was not circumcised, did not - he would be "cut off from his people".

There's a funny story in the Bible about Paul & Timothy.  Paul circumcised Tim and, as per the ritual, had to suck the bleeding blood.  Paul didn't like that so he made the rule that Gentiles don't have to get circumcised to become Christians.  The main reason for Tim's circumcision was that it was the custom for Jews to whip out their penises when meeting other Jews to show that they were members of the clique.  So Tim had to get circumcised in order to be accepted as a member when he went on his missionary trips.