Green’s Dictionary of Slang

milker’s calf n.

[SE milker’s calf, a calf that is still with its mother]

(Aus.) a petted, favourite child, a ‘mother’s boy’.

[Aus]‘Rolf Boldrewood’ Robbery Under Arms (1922) 2: I used to laugh at him, and call him a regular old crawler of a milker’s calf.