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