c. 1200, "large, strong rope or chain used on a ship," from Old North French cable, from Medieval Latin capulum "lasso, rope, halter for cattle," from Latin capere "to take, seize," from PIE root *kap- "to grasp."
Technically, in nautical use, a rope 10 or more inches around, to hold the ship when at anchor; in non-nautical use, a rope of wire (not hemp or fiber). Given a new range of senses in 19c. in telegraphy (1850s), traction-railroads (1880s), etc. Meaning "message received by telegraphic cable" is from 1883, short for cable message (1870), cablegram (1868), cable dispatch (1864). Cable television first attested 1963; shortened form cable in this sense is from 1970.
Speed, speed the Cable; let it run,
A loving girdle round the earth,
Till all the nations 'neath the sun
Shall be as brothers at one hearth;
[T. Buchanan Read, "The Cable," 1858]