The idiom “ put one’s back up ” means to make someone annoyed, defensive, or irritated. Literal meaning: Imagine a cat arching its back when it feels threatened or provoked. The raised back signals tension and hostility. Figurative meaning: When someone says a remark or behaves in a way that “puts your back up,” it means they’ve triggered your irritation or made you bristle with defensiveness. In short, this English expression describes the shift from calm to annoyed—just like a cat suddenly arching its back. Origin or Background The idiom “put one’s back up” dates back to the 18th century and is rooted in animal behavior, particularly cats. When cats feel threatened, they instinctively arch their backs, fluff their fur, and appear larger to ward off danger. The earliest recorded use in English writing appears in the late 1700s. It reflects a broader cultural tendency to borrow imagery from animals to describe human emotions—similar to sayings like “ raining cats and dogs ” or “le...