A male is called a hob, and a female is a jill.  To some people,
neutered males are gibs and neutered females are sprites , but these
are new terms and aren't as commonly used.  A baby ferret of either
sex is a kit.

The most commonly accepted phrase for a group is "a business of
ferrets".  Some people spell it "busyness" instead.  Another
possibility, "fastening" or "fesnyng," is thought to be due to a
misreading of "bysnys" long ago.