Knuckles...semantics

Talking with my nephew after Thanksgiving dinner was a laugh. He was telling me about a concert he went to and said the following:

Nephew: The singer from the band knuckle-touched me

Me: He what you?

Nephew: Knuckle-touched, he knuckle-touched me.

Me: What's knuckle-touching - you mean fist-bump?

Nephew: Yeah, same thing.

Me: I dunno - I've never heard the term knuckle-touching, fist bump...sure, I know what that is. Knuckle touching sounds like something some perv would get in trouble from Child Services for doing - like big trouble, hard time...you know, have to register with the authorites wherever he lives from now on kinda trouble.
"Can you show us on the doll where he knuckle-touched you?...Do you feel safe at home? Does anyone try to knuckle-touch you?...are you afraid of being knuckle-touched?...You know that knuckle-touching is wrong right?...it's not your fault, you can tell us if someone tries to....

Nephew (laughing): Yeah...I got it, it does sound kinda creepy.

Me: It sounds VERY creepy, you kidding??

This became a running joke the rest of the visit - and for the record, I still think it's hilarious. Then again, no one has ever tried to knuckle touch me. Fist bump, well...yeah, a time or two. I have another friend who is one of my coworkers, sometimes one of my bosses. She has a thing where you think she's going to fist-bump you, but instead she grabs your fist. I think she was confused, maybe trying to be hip - but I can't say for sure. She asked me once, "What's that fist bump that I do called?", to which I jokingly replied, "Awkward." I think I'd really rather people just shake hands. Oh well, what do I know?