quicksilver

the word quicksilver is a calque, or literal translation, of the latin term "argentum vivum," meaning "living silver." this vividly describes the metal mercury's unique property of being a shiny, silver-colored liquid that moves with a lively, unpredictable fluidity at room temperature. the old english "cwic," meaning alive or lively, was combined with "seolfor," the term for the precious metal, to create this descriptive compound. over time, the literal name for the element also gave rise to a figurative adjective sense, capturing anything that displays similarly rapid and elusive motion.

Structure: quick (fast) + silver (shiny metal) quick (old english, meaning "alive, living, fast"); silver (old english, meaning the metallic element, noted for its bright, pale grey colour and liquidity).