Well, I think a majority of them just kept the old world names they had originally, more or less. Maybe with the occasional qualifier, like New Vegas or New Reno.

...Then there are places like the Boneyard, which is, ah, fairly aptly named for the ruin it was left in, before settlers began rebuilding there.

[ There probably are plenty of hopeful little settlements out there, with cute, optimistic names - but Arcade isn't so knowledgeable about geography as to rattle off more than the broad strokes. ]

I guess we don't all have the same sunny outlook, where I'm from.