plus fours vs knickers

plus fours and knickers both are nouns.

Word	Noun	Adjective	Verb	Adverb
plus fours	Yes	No	No	No
knickers	Yes	No	No	No

As nouns, knickers is a hypernym of plus fours; that is, knickers is a word with a broader meaning than plus fours:

plus fours: men's baggy knickers hanging below the knees; formerly worn for sports (especially golf)
knickers: (used in the plural) trousers ending above the knee

Other hypernyms of plus fours include breeches, knee breeches, knee pants, knickerbockers.

plus fours (noun)	knickers (noun)
men's baggy knickers hanging below the knees; formerly worn for sports (especially golf)	(used in the plural) underpants worn by women
	(used in the plural) trousers ending above the knee