Word Origin & History
gravy1381, from O.Fr. grané (with -n- misread for -u- -- the character used for -v- in medial positions in words in medieval manuscripts) "sauce, stew," probably originally "properly grained, seasoned," from L. granum "grain, seed." Meaning "money easily acquired" first attested 1910; gravy train (1927)
was originally railroad slang for a short haul that paid well.