She told him to 'keep/stay mum' about the project. [=she told him not to tell anyone about the project]
We want her birthday party to be a surprise, so 'mum's the word'. [=don't tell her about the party]
I'd like to know how much they paid, but they've been 'mum' on that subject.
(..) There's another day every day. Every day's a learning day, boy. Where is everyone? Where you been sleeping, Gen? Rip's been pulled out. Rip's mum said you'd been sleeping up at the monument. Gen! Kia or a. Are you Rip's mother? Hi, my name is Genesis Potini. I'm his chess coach. (..)2014 The Dark Horse
(..) - No! No! No! - Yeah! Yeah! Shut up! Yes, it is, 'cause she's my next-door neighbour. Thanks. Mum, can Gen come in when we get home? I think Gen's got his own stuff to do tonight, hon. - Yeah! - Okay. - Thank you, though. (..)2014 The Dark Horse