"act of flowing or issuing from an origin; emission; radiation; what issues, flows, or is given out from any substance or body;" 1560s, from Late Latin emanationem (nominative emanatio), noun of action from past-participle stem of Latin emanare "flow out, spring out of," figuratively "arise, proceed from," from assimilated form of ex "out" (see ex-) + manare "to flow," from PIE root *ma- (3) "damp."