extravagance (n.)

1640s, "an extravagant act," from French extravagance, from Late Latin extravagantem (see extravagant). Specifically of wasteful spending from 1727. Meaning "quality of being extravagant" is from 1670s. Extravagancy, "a wandering," especially "a wandering from the usual course," is attested from c. 1600, now rare.