Selcouth
He drew the inspiration first from the Jewish tradition - intended for them as a means of authenticating one’s desire for conversion.
Hannibal likes to think his own reasons are much the same.
Hannibal is 17, in college under a false age and making ends meet by selling his company to those willing to expend the patience and money. Will Graham doesn't want a rentboy. But what he wants, in buying Hannibal over and over, is something the young man can't quite figure out yet.