Uh
I really don’t think Genos’ human name is… Genos? It doesn’t sound like a human name, much less a Japanese one since almost all the characters have Japanese names(if you’re talking about King, that’s technically his code name.)
My guess is that he made the name up for himself. A fifteen-year old boy would make a name punning on genocide, since that’s what his current self occurred from.
In the manga he’s not really subtle about it either LOL
He also introduces himself in the manga by saying ‘they call me genos’
So I think I’m going to agree that was probabllyyyy not his human name.
The shirt in the manga was why I first started thinking about it in the first place ehhh An anon sent in a suggestion that it might be GenOS as in OS as in the phone/computer systems(similar to iOS). That’s a solid thought too, since cyborgs need, uh, a lot of computing. My reply didn’t go through so I might as well put it here(thanks anon!).