Why is the ninth month called September?
1510s, "to send off in a hurry," from a word in Spanish (despachar "expedite, hasten") or Italian (dispacciare "to dispatch"). For first element, see dis-. The exact source of the second element has been proposed as Vulgar Latin *pactare "to fasten, fix" or *pactiare, or as Latin -pedicare "to entrap" (from Latin pedica "shackle;" see impeach); and the Spanish and Italian words seem to be related to (perhaps opposites of) Old Provençal empachar "impede." See OED for full discussion. Meaning "to get rid of by killing" is attested from 1520s. Related: Dispatched; dispatching. As a noun, from 1540s, originally "dismissal;" sense of "a message sent speedily" is first attested 1580s.