Charmeleon

In English, Charmeloen is made up of char and chameleon.

In exactly the same way for Charmander, char is a word meaning to burn or reduce to charcoal. This fits perfectly with the fire and flame motif.

Chameleon is an actual reptile of which I had many in my back garden growing up. The official dictionary definition describes a chameleon as any of numerous Old World lizards of the family Chamaeleontidae, characterized by the ability to change the color of their skin.

Personally, I like the way the word char fits so snuggly inside chameleon allowing the animal name to evolve by adding nothing more than an extra r to the word to give us the English name.

In comparison, Charmeloen's Japanese name is extremely literal as the Katakana リザード (rizādo) is the Japanese pronunciation of the English word lizard.

The English name still contains the reference to Charmeleon's fiery nature but it's curious that the Japanese has dropped it in favour of such a literal name.