I got lazy and didn't want to type out "Raphael", so I shortened it to "Raph" as my character's name, only to get a "Don't. Just, don't." message.
I decided to goof around with the mechanic, and found lots of different things it wouldn't let me use as a name.
As far as I could tell, nothing sexual, and most body-parts were a no. It also refused most of the 2 letter suggestions I made, but allowed some. It refused most 3 letter suggestions I made, but allowed some. It refused some four letter suggestions, but accepted most.

I'm just curious as to why it works this way, and why you implemented it?

(This is probably something you'd never thought anyone would bring up lol)