In English, 'butterfly' sounds warm, and kinda tasty (see 'butternut' and 'butter popcorn'). In French, 'le papillon' sounds, well, typically French and limp-wristed. In German, DER SCHMETTERLING sounds like something that could do you serious damage. It sounds like it would casually flap towards your face, then slap you in it with its 10" schlong. Not to be fucked with.
"Hey man, did you see that schmetterling just now?"
"Yeah, my face still hurts."
"Don't make me call the schmetterlings to sort you out."