ferret vs ferret out

ferret is a noun but ferret out is not a noun.

Word	Noun	Adjective	Verb	Adverb
ferret	Yes	No	Yes	No
ferret out	No	No	Yes	No

As verbs, ferret and ferret out are synonyms defined as:

ferret and ferret out: search and discover through persistent investigation

ferret (noun)	ferret out (noun)
domesticated albino variety of the European polecat bred for hunting rats and rabbits
musteline mammal of prairie regions of United States; nearly extinct

ferret (verb)	ferret out (verb)
search and discover through persistent investigation	search and discover through persistent investigation
hunt with ferrets
hound or harry relentlessly