extravagant (adj.)

"uncertain as to specifics," 1540s, from French vague "empty, vacant; wild, uncultivated; wandering" (13c.), from Latin vagus "strolling, wandering, rambling," figuratively "vacillating, uncertain," perhaps from PIE *Huog-o-  and cognate with Old Norse vakka "to stray, hover," Old High German wankon "to totter, stagger," Old High German winkan "to waver, stagger, wink," Old English wincian "to nod" [de Vaan]. Related: Vagueness.

1640s, "an extravagant act," from French extravagance, from Late Latin extravagantem (see extravagant). Specifically of wasteful spending from 1727. The 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. Middle English could express the idea by to-mochelhede "excess, extravagance, 'too-much-hood' " (mid-14c.).