RichThesaurus
give the game away
vs
let the cat out of the bag
give the game away
verb
To mistakenly reveal a secret.
let the cat out of the bag
verb
To disclose a secret; to let a secret be known, often inadvertently.
How often have the words
give the game away
and
let the cat out of the bag
occurred in a corpus of books?
(source:
Google Ngram Viewer
)