Green’s Dictionary of Slang

(Aus.) a euph. synon. of up your arse! excl.

1950		in J. Cleary Just Let Me Be in DSUE (1984).
1952		M.F. Caulfield Black City 44: ‘Flynn, you bitch’s bastard, look what you’ve done?’ ‘Up your jersey,’ said Flynn.
1954		J.E. Macdonnell Jim Brady 15: We snuck alongside and called on ’em to surrender. Not they! Up y’r jumper, f’r ours, they shouted in their own lingo.
1979		D. Maitland Breaking Out 6: ‘Up your gumboots,’ he muttered.