Nicknames

So I have started calling my children Zerg and Zork both used interchangeably. The question I keep getting is why? and where did these names come from? Do you remember the evil emperor Zerg from Toy Story? That is Kaylie....no explanation necessary....except when she's being sweet and adorable which really does still happen! (in glimpses). And why do I call sweet innocent Ashley these names? Because she grins huge every time I say them so maybe she just likes the ZZ sound? Who knows? I'm not very good at nicknames if you couldn't already tell but I come by it honestly! My sister calls her little boy doodoo.....Where did that come from? No, not from poop, but from dude! But if you didn't know....what would you think???