Smell a Rat

First documented in the English poet John Skelton's 1540 poem "The Image of Ipocrysy," which pairs the phrase directly with cats: "But then beware the catte; For yf they smell a ratt, They grisely chide and chatt." The most repeated theory is straightforward: cats hunt largely by smell and can sense a nearby rat long before they see one, an image transferred naturally to a person sensing trouble they can't yet prove. A rival theory points instead to rat-catching terriers, especially popular from the early 1800s onward. A third, less convincing theory suggests the phrase is a garbled mistranslation of an old German expression, "unrath wittern" (to scent mischief), reshaped into "eine ratte wittern" (to smell a rat).