Curiosity killed the cat, Being too inquisitive can lead to trouble.
Let the cat out of the bag, To reveal a secret, often unintentionally.
Word Origin
Language
Old English
Original word
catt
Originally meant
domesticated feline
Background
The word 'cat' comes from the Old English 'catt', which is derived from the Late Latin 'cattus'. It has been used in English since the early Middle Ages to refer to the domesticated animal we know today.