valise vs overnight case

valise and overnight case both are nouns.

Word	Noun	Adjective	Verb	Adverb
valise	Yes	No	No	No
overnight case	Yes	No	No	No

As nouns, overnight case is a hypernym of valise; that is, overnight case is a word with a broader meaning than valise:

valise: a small overnight bag for short trips
overnight case: a small traveling bag to carry clothing and accessories for staying overnight

Other hypernyms of valise include overnight bag, overnighter.

valise (noun)	overnight case (noun)
a small overnight bag for short trips	a small traveling bag to carry clothing and accessories for staying overnight