Why do men in medieval tales cut each other's hair and trim each other's beards?

Question

I know it has something to do with sealing a bond of kinship. I'd like some source that discusses it and might give me some more details. Maybe there's a castration metaphor involved? In particular, I'm dealing with Welsh tales that have Arthurian references. Help! My research paper's due tomorrow night and I can't find an answer to this one little detail. I'll proceed without it, but would like some more insight.

Answer 1

Hair was an integral part in many folklore spells for controlling peoples' actions, and so allowing someone else to cut your hair or trim your beard was considered a form of showing the highest level of trust and confidence in a person.

Answer 2

No one had yet invented the "barber shop."