free house vs gin mill

free house and gin mill both are nouns.

Word	Noun	Adjective	Verb	Adverb
free house	Yes	No	No	No
gin mill	Yes	No	No	No

As nouns, gin mill is a hypernym of free house; that is, gin mill is a word with a broader meaning than free house:

free house: a public house that is not controlled by a brewery and so is free to sell different brands of beer and ale
gin mill: tavern consisting of a building with a bar and public rooms; often provides light meals

Other hypernyms of free house include pothouse, pub, public house, saloon, taphouse.

free house (noun)	gin mill (noun)
a public house that is not controlled by a brewery and so is free to sell different brands of beer and ale	tavern consisting of a building with a bar and public rooms; often provides light meals