crawler vs bootlicker

crawler and bootlicker both are nouns.

Word	Noun	Adjective	Verb	Adverb
crawler	Yes	No	No	No
bootlicker	Yes	No	No	No

As nouns, bootlicker is a hyponym of crawler; that is, bootlicker is a word with a more specific, narrower meaning than crawler:

crawler: a person who tries to please someone in order to gain a personal advantage
bootlicker: someone who humbles himself as a sign of respect; who behaves as if he had no self-respect

Other hyponyms of crawler include apple polisher, fawner, groveler, groveller, truckler, goody-goody.

crawler (noun)	bootlicker (noun)
terrestrial worm that burrows into and helps aerate soil; often surfaces when the ground is cool or wet; used as bait by anglers	someone who humbles himself as a sign of respect; who behaves as if he had no self-respect
a person who tries to please someone in order to gain a personal advantage
a person who crawls or creeps along the ground