late 14c., "filled (with something); completely full, filled to satisfaction," from Old French replet "filled up" (14c.) and directly from Latin repletus "filled, full," past participle of replere "to fill; fill again, re-fill," from re- "back, again" (here perhaps an intensive prefix based on the notion of "fill repeatedly," thus "fill completely;" see re-) + plere "to fill" (from PIE root *pele- (1) "to fill"). Related: Repleteness.
late 14c., replecioun, "eating or drinking to excess," also "state of being replete, fact or condition of being filled up," from Old French repletion, replection (early 14c.) and directly from Late Latin repletionem (nominative repletio) "a filling up, complement," noun of action from past-participle stem of replere "to fill" (see replete). Meaning
also brain-storm, by 1861 as a colloquial term for "fit of acute delirious mania; sudden dethronement of reason and will under stress of strong emotion, usually accompanied by manifestations of violence," from brain (n.) + figurative use of storm (n.).
The sense of "brilliant idea, mental excitement, fit of mental application," is by 1934 and seems to have evolved from the earlier sense:
Modern radio broadcasting is replete with examples of the resourcefulness, daring and hair-trigger thinking of the men who handle the big news breaks and special programs for the networks — the "brainstorm boys" the announcers and engineers call them. Eye-witness accounts of federal agents surrounding a gang lair, word pictures of dust storms, stratosphere flights, floods and fires — these are but a few of the programs brought to radio audiences by the brainstorm squad. [Popular Mechanics, July 1936]
The verbal meaning "make a concerted attack on a problem, involving spontaneous ideas," is by 1947. Related: Brainstormed; brainstorming.