1907, "the action of seeing by means of Hertzian waves or otherwise, what is existing or happening at a place concealed or distant from the observer's eyes" [OED]; in theoretical discussions about sending images by radio transmission, formed in English or borrowed from French télévision, from tele- + vision. Other proposals for the name of this then-hypothetical technology were telephote (1880) and televista (1904). The technology was developed in the 1920s and '30s. Nativized in German as Fernsehen.
Meaning "a television set" is from 1955. Shortened form TV is from 1948.