pimpernel

The word "pimpernel" begins as the name of a small wildflower, most often the scarlet pimpernel, Anagallis arvensis. The plant became well known for the way its flowers close when the light fades or wet weather is near, which is why people called it the "Poor Man's Weather-glass." Because it seems to shut itself away when conditions change, the flower came to suggest caution, secrecy, and something that is hard to pin down.

Its strongest cultural meaning comes from Baroness Orczy's 1905 adventure novel, The Scarlet Pimpernel. In that story, Sir Percy Blakeney seems harmless and shallow in public, but in secret he rescues French aristocrats from the guillotine during the French Revolution. He escapes again and again through disguise, planning, and nerve, and he leaves behind a calling card with the little red flower on it.

Because of that famous story, the word can also suggest an elusive rescuer, a secret champion, or someone who moves in disguise and is hard to catch. This is not a very common dictionary meaning on its own; it is mainly an echo of The Scarlet Pimpernel and works best in literary, playful, or dramatic contexts. When people use it this way, they usually mean someone whose courage is hidden behind an ordinary or misleading appearance.

So the word carries two linked ideas: a small flower that closes itself up, and a legendary figure who slips out of sight while doing brave things. In modern English, the flower sense is direct and literal, while the hero sense is usually an allusion to the novel. That mix of nature, secrecy, and adventure is what gives the word its lasting charm.