1794, "semaphor apparatus" (hence the Telegraph Hill in many cities), literally "that which writes at a distance," from French télégraphe, from télé- "far" (from Greek tele-; see tele-) + -graphe (see -graphy). The signaling device had been invented in France in 1791 by the brothers Chappe, who had called it tachygraphe, literally "that which writes fast," but the better name was suggested to them by French diplomat Comte André-François Miot de Mélito (1762-1841). First applied 1797 to an experimental electric telegraph (designed by Dr. Don Francisco Salva at Barcelona); the practical version was developed 1830s by U.S. inventor Samuel F.B. Morse (1791-1872). Meaning "telegraphic message" is from 1821. Related: Telegraphy.
1805, from telegraph (n.). Figurative meaning "to signal one's intentions" is first attested 1925, originally in boxing. Related: Telegraphed; telegraphing.