Green’s Dictionary of Slang

(Aus.) frightened, terrified; thus suffering a bout of diarrhoea, engendered by fear.

1944		J. Devanny By Tropic Sea and Jungle 162: The croc disappears, and there’s Ernest, standing up to his waist in the water … scared as hell, but too game to come out … So my dad goes in. He’s a bit sterky too [OED].
1953		Baker Aus. Speaks.