keep mum vs dummy up

keep mum and dummy up both are verbs.

Word	Noun	Adjective	Verb	Adverb
keep mum	No	No	Yes	No
dummy up	No	No	Yes	No

As verbs, keep mum and dummy up are synonyms defined as:

Other synonyms of keep mum include be quiet, belt up, button up, clam up, close up, shut up.

keep mum (verb)	dummy up (verb)
refuse to talk or stop talking; fall silent	refuse to talk or stop talking; fall silent
	make a dummy of