also hook-up, connection, 1903, from verbal phrase hook up, which is attested from 1825 in reference to yarn; 1925 as establish a link with. The noun is from 1922 of radio sets, later of television broadcasts. Modern slang verbal sense of to meet for sex is attested by 2003.

When did the term hooking up?

In 1930, the term became specific, as a national hook-up came to denote a radio network. As a verb, to hook up has for a century also meant to marry, a synonym of to get hitched, as a horse is to a wagon. But not until the 1980s did the meaning change to a less formal sexual involvement.