overnight case vs traveling bag

overnight case and traveling bag both are nouns.

Word	Noun	Adjective	Verb	Adverb
overnight case	Yes	No	No	No
traveling bag	Yes	No	No	No

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

overnight case: a small traveling bag to carry clothing and accessories for staying overnight
traveling bag: a portable rectangular container for carrying clothes

Other hypernyms of overnight case include bag, grip, suitcase, travelling bag.

overnight case (noun)	traveling bag (noun)
a small traveling bag to carry clothing and accessories for staying overnight	a portable rectangular container for carrying clothes