What does one do, in terms of abbreviation, with characters that have large first names. Are there certain names that should be abbreviated? Is it okay to do it during narration? Must it be kept up if used in the narrative?
They could've called him "Wandering Soul" which is what it supposedly translates to, or "Soul". The character who called him "Kevin" didn't bother to figure out the name's meaning and went with with something that started and ended the same.
Names are arbitrary signifiers, so as long as they all use the same one it's a perfectly valid solution. I think the guy expecting to be referred to by the silly name is the dumb one.
How is he dumb? I never said he hated the nickname the other characters gave him. Besides the "silly name" is his actual name, his own kind call him by that name.
Since they speak to each other, it's obvious they would've hear him pronounce his name and give him a mispronounced name instead of a completely renaming him.
Most people who have a name not suitable for use by the people around them offer an alternative. If they don't, then they get one assigned to them. I see nothing dumb about that.