Green’s Dictionary of Slang

1. (orig. Aus.) the head.

1944		J. Cary Horse’s Mouth (1948) 59: I am upset, in fact; only because I can’t hit them all on the neddy.
1949		R. Park Poor Man’s Orange 234: Who’da thought it, eh, and her with the stren’th of ten when it comes to bashing johns over the ned.

2. (Aus.) in a game of two-up, the head side of the coin.

1999

G. Seal Lingo 150: Bets are won or lost on whether the result is two heads (skulls, nuts, neds); two tails (two micks), or one of each (ones).