lemming vs gnawer

lemming and gnawer both are nouns.

Word	Noun	Adjective	Verb	Adverb
lemming	Yes	No	No	No
gnawer	Yes	No	No	No

As nouns, gnawer is a hypernym of lemming; that is, gnawer is a word with a broader meaning than lemming:

lemming: any of various short-tailed furry-footed rodents of circumpolar distribution
gnawer: relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing

Other hypernyms of lemming include rodent.

lemming (noun)	gnawer (noun)
any of various short-tailed furry-footed rodents of circumpolar distribution	relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing