As a native English speaker, every time I see the name "Wanko" it makes me giggle because it's like calling yourself Wankster or Wanky or something like that.
But finally seeing it written right next to Nyanko I finally understand now. Nyan is meow, Wan is woof, and the ko suffix can loosely be translated in this context as "y". So the author has two friends who use the pseudonyms Meowy and Woofy.