A jockstrap or athletic supporter is an undergarment for men. It consists of an elastic band round the waist, a triangle to cover the genitals and two strings from the bottom of the triangle to the waistband that hold the triangle in position without going through the crotch.
It is primarily intended to support the genitals during strenuous athletic activity, and may also be used by ballet dancers who wear very close-fitting ballet tights. Worn on its own, its revealing nature makes it a popular fetish among gay men and some women. Making someone wear one in public may be a humiliation technique.
The name (first recorded in 1886) means a strap to support the jock, a dialect word for the penis. It has no connection with Jock as a slang word for a Scotsman. The name athletic supporter was first recorded in 1927.