Word Origin & History
c.1300, from O.Fr. en gros "in bulk, in a large quantity, at wholesale," as opposed to en detail. Figurative sense of "absorb the whole attention" is first attested 1709. A parallel engross, meaning "to write (something) in large letters," is from Anglo-Fr. engrosser, from O.Fr. en gros "in large (letters)."
Related: Engrossed; engrossing.