Ribbit is the sound a frog makes, or at least the sound we use in English to describe a frog's croaking call. Real frogs make many different sounds depending on their species: some chirp, some click, some make deep rumbling sounds, and some do sound something like “ribbit.” But in English, when we want to imitate a frog, we say ribbit.

The word is onomatopoeia, which means it's spelled to sound like what it represents, similar to how we write buzz for a bee's sound or splash for water. Different languages use different words for frog sounds: in Japanese, frogs say “kero kero,” and in Korean, they say “gae-gool, gae-gool.”