HP,
'Jumper' is a good old aussie word. Football players in Oz wear a 'jumper' and they often say that they 'play for the jumper'! Then again a 'jersey' is a breed of dairy cow, so I'm not sure how you would wear that. Carrying a jersey cow around while you play golf might be a bit testing.
It just depends on where you come from. Believe it for not, not everyone in the world lives in the USA!! Just saying!
Bob from downunder..