shelver vs worker

shelver and worker both are nouns.

Word	Noun	Adjective	Verb	Adverb
shelver	Yes	No	No	No
worker	Yes	No	No	No

As nouns, worker is a hypernym of shelver; that is, worker is a word with a broader meaning than shelver:

shelver (noun)	worker (noun)
a worker who puts things (as books) on shelves	sterile member of a colony of social insects that forages for food and cares for the larvae
	a person who works at a specific occupation
	a member of the working class (not necessarily employed)
	a person who acts and gets things done