overnight bag vs travelling bag

overnight bag and travelling bag both are nouns.

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

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

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

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

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