Actually it was originally "champing" – to grind or gnash teeth. The "chomping" (to bite) alternative cropped up more recently as people misheard and misunderstood, but it's generally accepted as an alternative now.
It’s actually accepted as the primary now and telling people about “champing” is just seen as archaic.
It’s actually accepted as the primary now and telling people about “champing” is just seen as archaic.