gaoler vs keeper

gaoler and keeper both are nouns.

Word	Noun	Adjective	Verb	Adverb
gaoler	Yes	No	No	No
keeper	Yes	No	No	No

As nouns, keeper is a hypernym of gaoler; that is, keeper is a word with a broader meaning than gaoler:

Other hypernyms of gaoler include law officer, lawman, peace officer.

gaoler (noun)	keeper (noun)
someone who guards prisoners	one having charge of buildings or grounds or animals
	someone in charge of other people