simmer down vs settle down

simmer down and settle down both are verbs.

Word	Noun	Adjective	Verb	Adverb
simmer down	No	No	Yes	No
settle down	No	No	Yes	No

As verbs, simmer down and settle down are synonyms defined as:

simmer down and settle down: become quiet or calm, especially after a state of agitation

Other synonyms of simmer down include calm, calm down, chill out, cool it, cool off.

simmer down (verb)	settle down (verb)
become quiet or calm, especially after a state of agitation	become settled or established and stable in one's residence or life style
	become quiet or calm, especially after a state of agitation
	settle into a position, usually on a surface or ground