flux (n.) Look up flux at Dictionary.com
late 14c., from Old French flus "flowing, rolling, bleeding," or directly from Latin fluxus "flowing, loose, slack," past participle of fluere "to flow" (see fluent). Originally "excessive flow" (of blood or excrement); an early name for "dysentery;" sense of "continuous succession of changes" is first recorded 1620s. The verb is early 15c., from the noun.