1510s, "to send off in a hurry," from Sp. despachar "expedite, hasten," probably opposite of O.Prov. empachar "impede," either from Gallo-Romance *impactare, frequentative of L. pingere "dash against," or ult. from L. pedica "shackle" (see impeach). Meaning "to get rid of by killing" is attested from 1520s. Noun sense of "a message sent speedily" is first attested 1580s. Related: Dispatched; dispatcher.