So I noticed one of my databases was added to my Create menu, which is neat - it shows up as "New Wiki Page in Wiki". But can I disable the "in Wiki" part of it? I can get why it's there - maybe someone would have a "New Car in Garage" or something like that, but there really should be an option to disable the "in x database" part of it.

That’s the singular string you set up for each database in the database settings. The records need to be called something – you can’t just leave that blank. Just like “post”, “topic”, “article” … Those strings will appear in many places, not just the Create menu. 

Yeah, I get that - I mean, though, is there any way I can make it so that in the Create menu it just says "New Wiki Page?" The "New Wiki Page in Wiki" seems a tad odd.

Well, there is definitely no setting for that. Haven’t checked whether a change would require template or core file edits. 
It’s probably the easiest thing to just choose terms that work together better. ;-)

'New page in Wiki'....problem solved.