Pennyroyal

This is a real curiosity of blundering derivation. The Latin word is pulēcium, the flea destroyer, from pulex, a flea, softened into pulègium, and corrupted into the English-Latin puleʹ-regium. “Pule,” changed first into puny, then into penny, gives us “penny-regium,” whence “penny-royal.” The French call the herb pouliot, from pou (a louse or flea).