shoulder bag vs pocketbook

shoulder bag and pocketbook both are nouns.

Word	Noun	Adjective	Verb	Adverb
shoulder bag	Yes	No	No	No
pocketbook	Yes	No	No	No

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

shoulder bag: a large handbag that can be carried by a strap looped over the shoulder
pocketbook: a container used for carrying money and small personal items or accessories (especially by women)

Other hypernyms of shoulder bag include bag, handbag, purse.

shoulder bag (noun)	pocketbook (noun)
a large handbag that can be carried by a strap looped over the shoulder	a container used for carrying money and small personal items or accessories (especially by women)
	pocket-sized paperback book
	a pocket-size case for holding papers and paper money
	your personal financial means