1590s, "pertaining to management of a household," perhaps shortened from economical, or else from French économique or directly from Latin oeconomicus "of domestic economy," from Greek oikonomikos "practiced in the management of a household or family" (also the name of a treatise by Xenophon on the duties of domestic life), hence, "frugal, thrifty," from oikonomia "household management" (see economy (n.)). Meaning "relating to the science of economics" is from 1835 and now is the main sense, economical retaining the older one of "characterized by thrift."
