Smell a Rat (Origin)

What Is the Origin of the Saying "Smell a Rat"?

The term "smell a rat" means to suspect something is wrong or to suspect someone of betraying the group (i.e., of being an informer).

Examples of Use:

• Why have they only sent the deputy leader to the meeting? I smell a rat.
• I smell a rat. The offer is too good to be true.
• Her husband has been working late a lot recently. She is starting to smell a rat.
• How did the protestors know about the product launch? The CEO smells a rat.
(Here, the idiom refers specifically to suspecting there is an informer.)

This idiom is very old. It originates from at least the 16th century as evidenced by its appearance in English poet John Skelton's 1540 poem "The Image of Ipocrysy":

• "But then beware the catte; For yf they smell a ratt, They grisely chide and chatt."

The saying "to smell a rat" comes from the idea of a cat hunting a rat. Just as a cat can smell that there is a rat nearby, so we can sense that something isn't quite right. The word "rat" is a metaphor for a something bad, which is hardly surprising given the plagues and diseases associated with rats.

Of note, a person in a group who secretly gives information to the authorities or an enemy is known as a "rat." Sometimes, "smell a rat" refers specifically to suspecting there is an informer in the group.

Competing Theory

Rats stink – dead rats even more so. This saying originates from the idea that we can tell a rat is present from its smell. Imagine someone moving furniture and looking in cupboards to find the source of the foul smell, a dead rat.

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