knee pants vs knickerbockers

knee pants and knickerbockers both are nouns.

Word	Noun	Adjective	Verb	Adverb
knee pants	Yes	No	No	No
knickerbockers	Yes	No	No	No

As nouns, knee pants and knickerbockers are synonyms defined as:

knee pants and knickerbockers: (used in the plural) trousers ending above the knee

Other synonyms of knee pants include breeches, knee breeches, knickers.

knee pants (noun)	knickerbockers (noun)
(used in the plural) trousers ending above the knee	(used in the plural) trousers ending above the knee