Technically a female crocodile is called a Cow crocodile, and the male one is a Bull crocodile.

"Crocodile cow" is more used with people on the know, scientists, schoolars, etc.

A way of knowing it´s a crocodile cow is seeing them laying eggs, or because they are, in size, way smaller than the bull crocodiles.

http://carnivoraforum.com/topic/10234794/1/

http://blog.oxforddictionaries.com/2016/04/male-and-female-animals/