eminence (n.)

c. 1400, "projection, protuberance;" early 15c., "high or exalted position," from Old French eminence or directly from Latin eminentia "a distinctive feature, conspicuous part," from eminentem (nominative eminens) "standing out, projecting," figuratively, "prominent, distinctive," from assimilated form of ex "out" (see ex-) + -minere, which is related to mons "hill" (from PIE root *men- (2) "to project").

As a title of honor (now only of cardinals) it is attested from 1650s. The original Éminence grise (French, literally "gray eminence") was François Leclerc du Trembley (1577-1638), confidential agent of Richelieu.