Green’s Dictionary of Slang

cacky n.

also cackie
[cack n.2 (1)]

human excrement.

[Aus]N. Keesing Lily on the Dustbin 48: One child ‘does its business’, talks of ‘binnie one’ or ‘binnie two’ or ‘number one’ and ‘number two’, and another ‘makes cackie’, or ‘poop’.
[UK]Partridge DSUE (8th edn) 172/1: since ca. 1880.