Yours, Etc.: Origins and Uses of 8 Sign-Offs
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.
The discharge of large quantities of fluid material from the body, especially the discharge of watery feces from the intestines.
Material thus discharged from the bowels.
The rate of flow of fluid, particles, or energy through a given surface.