lockman vs skilled workman

lockman and skilled workman both are nouns.

Word	Noun	Adjective	Verb	Adverb
lockman	Yes	No	No	No
skilled workman	Yes	No	No	No

As nouns, skilled workman is a hypernym of lockman; that is, skilled workman is a word with a broader meaning than lockman:

Other hypernyms of lockman include skilled worker, trained worker.

lockman (noun)	skilled workman (noun)
a worker in charge of a lock (on a canal)	a worker who has acquired special skills