It really depends on the cats behaviour really like my 1st cat we called him nutter as he used to run around all day and never get tired,
OR the names can be based on what they look like, like my two cats have names that reffer to what they look like,
like, Bruiser( he's black and white) as he has a black nose and looks very butch,
and Smokey( I named her) She is black from head to toe.
It's very hard to belive their brother and sister as their apperance is totally differant and their personallites are totally differant.
Just a few Ideas.