1) Get a word in edgeways/edgewise
-Monica was talking so much that nobody else could get a word in edgeways.
-Once Tom and Anna start talking, it's impossible to get a word in edgeways.
-Being a quick thinker helped Linda to get a word in edgeways in conversations.
Definition: join a conversation in which another is speaking continually and leaving little opportunity for others
Etymology: is a 19th century expression coined in the UK and alludes to edging sideways through a crowd, seeking small gaps in which to proceed through the throng.
2) Keep it under your hat
-There's going to be a surprise party for Lucy on Friday. But keep it under your hat for now.
-Anne is pregnant but keep the information under your hat since she doesn't want anybody to know just yet.
-Jane loves gossiping. She can't keep anything under her hat.
Definition: keep it secret
Etymology: The speculation is that putting an item under one's hat would be a way of hiding it. Such trickery is recorded, as in the collection of stories published as The Adventurer, 1793:
"By the sudden stroke of conjuration, a great quantity of gold might be conveyed under his hat."
3) The game is up
-The cheating student knew the game is up when the examiners came and escorted him out of the classroom.
-When the police were waiting for them inside the bank vault, the would-be robbers knew that the game was up.
-"The game is up," said the cop as he grabbed the shoulder of the pickpocket.
Definition: The illegal activity has been found out or has come to an end. Basically, it means 'we have seen through your tricks - your deceit is exposed.'
Etymology:
From Shakespeare's Cymbeline, 1611:
"Euriphile, Thou wast their nurse; they took thee for their mother,
And everyday do honour to her grave:
Myself, Belarius, that am Morgan call'd,
They take for natural father. The game is up."
*original meaning was 'the game is over - all is lost'