sweater (n.)

"woolen vest or jersey, originally worn in rowing," 1882, from earlier sweaters "clothing worn to produce sweating and reduce weight" (1828), plural agent noun from sweat (v.). As a fashion garment, attested from 1925. Earlier it meant "one who works hard" (1520s). Sweater girl is attested from 1940; Lana Turner (1920-1995) was the first, from her appearance in the film "They Won't Forget" (1937).