truckle vs suck up

truckle is a noun but suck up is not a noun.

Word	Noun	Adjective	Verb	Adverb
truckle	Yes	No	Yes	No
suck up	No	No	Yes	No

As verbs, truckle and suck up are synonyms defined as:

Other synonyms of truckle include bootlick, fawn, kotow, kowtow, toady.

truckle (noun)	suck up (noun)
a low bed to be slid under a higher bed

truckle (verb)	suck up (verb)
try to gain favor by cringing or flattering	try to gain favor by cringing or flattering
yield to out of weakness	take in, also metaphorically
	ingratiate oneself to; often with insincere behavior