Jersey is a crown dependency island of the UK where the people have been knitting great wool sweaters for centuries. These tight knit warm sweaters were initially used as an inner layer by rural seamen before evolving into common outerwear. Jersey sweaters spread about the UK and northern Europe as the country’s trading industry rose in prominence during the late 17th and early 18th centuries. Their popularity gained so much, the name “jersey” became synonymous with “sweater” in countries as far away as the United States during the 1850s. When American football developed, players needed strong, insular uniforms, and thick wool jerseys did the job..
Athletic jerseys bore increasingly little resemblance to their bulky
ancestral tops. Just as the name had become a synonym for sweater,
it soon became a synonym for athletic uniform. Lightweight baseball
shirts were often called “jerseys” despite being generally made of
flannel and incorporating short sleeves, buttons, and collars.
Canadian hockey sweaters began being called jerseys. Americans used
jerseys when they were playing football, then baseball, then hockey.