cotton up vs sidle up

cotton up and sidle up both are verbs.

Word	Noun	Adjective	Verb	Adverb
cotton up	No	No	Yes	No
sidle up	No	No	Yes	No

As verbs, cotton up and sidle up are synonyms defined as:

cotton up and sidle up: ingratiate oneself to; often with insincere behavior

Other synonyms of cotton up include cozy up, play up, shine up, suck up.

cotton up (verb)	sidle up (verb)
ingratiate oneself to; often with insincere behavior	ingratiate oneself to; often with insincere behavior