"water," late 14c., from Latin aqua "water; the sea; rain," from PIE root *akwa- "water." Used in late Middle English in combinations from old chemistry and alchemy to mean "decoction, solution" (as in aqua regia, a mix of concentrated acids, literally "royal water," so called for its power to dissolve gold and other "noble" metals). As the name of a light greenish-blue color, 1936.
