What does it mean..?

If he's trying to hide it, then obviously he has some embarassing or unsavory reason for doing it, I can't imagine what it could be other than unclean.

I don't know. Maybe it's itchy?

It means that he does't take bath regularly or probably he is more a shy person.

It doesn't mean anything. It's no different than a guy idlely fiddling with his beard or a girl twisting or chewing on a loose bit of hair.

Maybe there is some deep connection between them. Whatever the reason may be, it's not a uniquely guy reason.

we (the answerers) probably need more context. but. hairy guys have hair that goes all of the way from their belly buttons to the lower extremities. hair = scratching. dead skin cells build up, and then you nerves naturally send the signal to the brain that there is an itch in the area.

It's just a comfort thing.

Aren't we old enough to say the real word? Erection?