Difference between Shut Up and Keep Mum

SHUT UP vs KEEP MUM: ADJECTIVE

I don't believe it!, no way!
Of a person, to stop talking or (of a person or thing) making noise.
To put (an object) in a secure enclosed place.
To enclose (a person, animal or thing) in a room or other place so that it cannot leave.
To terminate (a business).
To close (a building) so that no one can enter.
Place in a place where something cannot be removed or someone cannot escape
Cause to be quiet or not talk
Refuse to talk or stop talking; fall silent

To not talk; especially keep silent about something that may be sensitive or secret.
Refuse to talk or stop talking; fall silent

Button up, Belt up, Dummy up, Lock away, Hush up, Still, Lock, Hush, Silence, Quieten, Put away, Close up, Lock in, Lock up, Be quiet

Unsecret, Marry off, Lie low, Dernful, Imperfect tense, Dishaunt, Pipe down, Swear off, Dummy up, Clam up, Button up, Belt up, Close up, Be quiet, Shut up

Confined, Lock away, Hush up, Dummy up, Clam up, Button up, Belt up, Still, Lock, Hush, Silence, Quieten, Close up, Lock in, Lock up

Shadowish, Let loose, Film clip, Unsecret, Marry off, Lie low, Dernful, Imperfect tense, Dishaunt, Pipe down, Dummy up, Clam up, Button up, Belt up, Close up

They must either put up or shut up.
His favorite sayings, back up, drop it, shut up.
Russia tells BRD, US, put up or shut up.
You told me to put up or shut up.
She shelf boston put up or shut up reficar.
The three marks of a good preachers are these: He stands up, speaks up, and knows when to shut up!
Saudi Arabia is a totalitarian state where my daughters are locked up, wrapped up and shut up.
Shut up, shut up, and take everything, disembodied code voice, take everything!
Poor women in psychological research: Shut up and shut out.
Shut up, dammit, all of you just shut UP!