calonkus, n. — Green’s Dictionary of Slang

calonkus n.

[? echoic of the ‘kalonk’ of hitting one’s head with a palm or fist]

(Aus.) a fool.

1949		R. Park Poor Man’s Orange 118: How would I know that some bullet-headed calonkus would leave a chair on the stairs?
1984		Partridge DSUE (8th edn) 175/2: late C.19–20.