It can also be onomatopoeia for eating something crispy. So, imagine a comic where a hamster is nibbling away at a cracker, then above that can be written:

*Knusper* *Knusper*

(basically *Crunch* *Crunch*)

But yeah, thanks for the rest of the explanation. I chose this username essentially at random when signing up here, but it’s been growing on me. Just a fun word in our language.