The word chameleon first showed up in English in 1340 CE in the Ayenbyte of Inwyt, a book we've already come across in the past. It was translated by Kentish priest Dan Michel of Northgate from French, and since he couldn't find an equivalent of the word cameleon, he simply wrote the Middle English predecessor of our current term, gamelos (due to further influence from French, this was later modified to look more familiar to us). The French word traces to Latin chamaeleon, from Ancient Greek khamaileon, with the same meaning. The root of the first part is the verb khamein, or "to be on the ground", and the second bit comes from leon, meaning "lion". So a chameleon is a "lion on the ground": the theory behind this is that it was so named because a chameleon's head crest vaguely resembles a lion's mane. Khamein is from Proto-Indo-European dheghm, meaning "earth", and leon could be non-IE in origin, but that's uncertain.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.