Why do zoologists name the bones/muscles of frogs like those of a human?

Zoologists name the bones/muscles of frogs like those of a human because frog skeletons are remarkably similar to human skeletons.

The frog has one "forearm" bone, the radio-ulna. Humans have two forearm bones, the radius and the ulna. Both frog and human have one "upper arm" bone, the humerus.