sweater (n.) Look up sweater at Dictionary.com
"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).