This is a very apt description for many reptiles, as they move around by crawling or slithering on their bellies. The word entered English in the late 16th century.
It's interesting to note that the word "reptile" wasn't initially used in the scientific sense that we use it today. It was first used to describe any animal that moved on its belly, including snakes, lizards, frogs, and even insects.
It wasn't until the 18th century that the term was used more specifically to describe the group of animals that we now know as reptiles, including snakes, lizards, turtles, crocodiles, and tuataras.