DISPATCH, or Despatch, to send off immediately, or by express; particularly in the case of the sending of official messages, or of the immediate sending of troops to their destination, or the like. The word is thus used as a substantive of written official reports of events, battles and the like, sent by ambassadors, generals, etc., by means of a special messenger, or of express correspondence generally. From the primary meaning of the prompt sending of a message, etc., the word is used of the quick disposal of business, or of the disposal of a person by violence; hence the word means to execute or murder. The etymology of the word has been obscured by the connexion with the Fr. dépêcher, and dépêche, which are in meaning the equivalents of the Eng. verb and substantive. The Fr. word is made up of the prefix de-, Lat. dis-, and the root which appears in empêcher, to embarrass, and means literally to disentangle. The Lat. origin of dépêcher and empêcher is a Low Lat. pedicare, pedica, a fetter. The Fr. word came into Eng. as depeach, which was in use from the 15th century until "despatch" was introduced. This word is certainly direct from the Ital. dispacciare, or Span, despachar, which must be derived from the Lat. root appearing in pactus, fixed, fastened, from pangere. The New English Dictionary finds the earliest instance of "dispatch" in a letter to Henry VIII. from Bishop Tunstall, commissioner to Spain in 1516-1517.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)