"flowing like honey, smoothly or sweetly flowing," c. 1600, from French mellifluent and directly from Late Latin mellifluentem (nominative mellifluens), related to mellifluus (see mellifluous). Related: Mellifluence.
early 15c., "sweet as honey, pleasing, sweetly or smoothly flowing" (of an odor, a style of speaking or writing, etc.), from Late Latin mellifluus "flowing with (or as if with) honey," from Latin mel (genitive mellis) "honey" (related to Greek meli "honey;" from PIE root *melit- "honey") + -fluus "flowing," from fluere "to flow" (see fluent). Related: Melifluously; melifluousness.
early 15c., "liquid, capable of flowing," from Old French fluide (14c.) and directly from Latin fluidus "fluid, flowing, moist," from fluere "to flow" (see fluent). Figurative use, of non-material things, "not fixed or rigid," from 1640s. Related: Fluidly.
mid-14c., "a plentiful flowing, an abundant supply," from Old French affluence, from Latin affluentia "affluence, abundance," literally "a flowing to," abstract noun from affluentem (nominative affluens) "flowing toward; abounding, rich, copious" (see affluent). The notion in the figurative Latin sense is of "a plentiful flow" of the gifts of fortune, hence "wealth, abundance of earthly goods," a sense attested in English from c. 1600. Latin affluentia is glossed in Ælfric's vocabulary (late Old English) by oferflowendnys.