To turn someone on is to arouse them sexually, or, in a milder and older sense, to excite their interest or enthusiasm for something. The phrase can describe a specific attraction, as in finding a particular look or manner appealing, or a general capacity for exciting someone, as in the related noun “a turn-on”. It sits alongside other body-and-emotion idioms as a fairly informal way of talking about desire, and it is used just as often to describe what fails to interest someone, in the negative form “turn off”.
What’s the origin of the phrase ‘turn someone on’?
The phrase begins as a piece of everyday mechanical language. “Turn on”, meaning to activate a switch or a mechanism, is recorded from 1833, the sort of phrase used of taps, lamps and later electrical devices. From that literal sense, a figurative use meaning “excite, stimulate, arouse” had developed by 1903, treating a person’s interest or feelings as something that could be switched on in the same way as a machine.
The specifically sexual meaning came later still, and belongs to the second half of the twentieth century. The slang historian Tom Dalzell, in Flappers 2 Rappers: American Youth Slang (1996), traces the sense of “a sexually arousing action” to the Hippie counterculture of the 1960s. Dalzell notes that closely related uses of “turn on”, meaning to take drugs or to become intoxicated, and also meaning to introduce someone to something they come to enjoy, are older, dating back to the Beat Generation of the 1950s. The two strands overlapped: turning someone on to drugs and turning someone on in the sexual sense grew up in the same slang culture within a couple of decades of each other, and both drew on the same underlying image of switching a person’s response on.
The noun form, “turn-on”, follows the same pattern. It appears only from 1968, and was first used specifically of psychedelic drugs before broadening to cover anything, sexual or otherwise, that a person finds exciting or appealing. Once the noun existed alongside the verb, “turn someone on” could be used just as naturally of music, a hobby or an idea as of a person, though the sexual sense has remained the one most people reach for first.