Why are frogs called tadpoles?

This is because a frog is not born a frog. Little heads are born. They are also called tadpoles because of their specific species. Then the tadpoles develop and gradually turn into a frog. Transformed individuals are sometimes called tadpoles, although this is not entirely correct. Also, this name stuck due to the incorrect name of frogs in films and cartoons. Although there is nothing wrong with that, unless of course you are a biologist or herpetologist, since the exact classification should be used by specialists.