The English idiom “curiosity killed the cat” is not as dark as it sounds and does not in fact involve the harming of any animals! The term is a fairly old-fashioned way of warning people about the way in which they behave.
The proverb is used when someone is being overly nosy and prying into the business of other people. It suggests that being overly curious and interested in the affairs of other people can be dangerous.
This expression has evolved over time and in fact when it was first coined in 1598 by the English playwright Ben Jonson it said,“care killed the cat” meaning that being overly sorrowful was dangerous. William Shakespeare who had seen Jonson’s play then coined his expression in 1599 in his play Much Ado About Nothing, where he wrote “What, courage man! What though care killed a cat, thou hast mettle enough in thee to kill care.” This expression, however, did not stick and the term changed over time to the way we know it today. It is not known exactly why this is but it is certain that the current expression derived from Jonson’s expression. The first recorded usage of the proverb in it’s current form can be found in James Allan Mair’s 1873 A handbook of proverbs: English, Scottish, Irish, American, Shakesperean, and scriptural; and family mottoes in which he cites it as a proverb with Irish origins though the reasons for this are unclear.
An example of this expression in use can be found in the novel The Resistance by Gemma Malley who writes, “More question. You know that curiosity killed the cat?”
Perhaps the definitive origins of this expression will never be found and we should stop investigating as this could be deemed as a case of “curiosity killed the cat.”