overnighter vs travelling bag

overnighter and travelling bag both are nouns.

Word	Noun	Adjective	Verb	Adverb
overnighter	Yes	No	No	No
travelling bag	Yes	No	No	No

As nouns, travelling bag is a hypernym of overnighter; that is, travelling bag is a word with a broader meaning than overnighter:

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

Other hypernyms of overnighter include bag, grip, suitcase, traveling bag.

overnighter (noun)	travelling bag (noun)
a small traveling bag to carry clothing and accessories for staying overnight	a portable rectangular container for carrying clothes
a guest who stays overnight