from The Century Dictionary and Cyclopedia
- Having a large wide mouth, like a frog's.
Sorry, no etymologies found.
The frog-mouthed poet looked at Maati and gestured pointedly to his own side.
"What is this?" the poet — the frog-mouthed Heshai-kvo, he had to be — demanded.
Max, rat-eyed and frog-mouthed, came forward propitiatingly.
Paul had had abominable luck all day, the only thing he landed being what we Bolderhead boys called a "grunter" -- a frog-mouthed fish of most unpleasant aspect and of absolutely no use as food.
It doesn't help that you are a thumbhead (your neck is the same width as your head, so you just look like a hairy thumb), but mostly it's that wide-eyed, frog-mouthed panting face.