aqua (n.) Look up aqua at Dictionary.com
"water," late 14c.; see aqua-. 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.