Green’s Dictionary of Slang

hotten up one’s copper v.

(N.Z.) to have something warm to eat and drink.

[Aus]Baker N.Z. Sl. 53: To hotten up one’s copper, to consume warm food or drink hot tea.
[NZ]McGill Reed Dict. of N.Z. Sl. 106: hotten up one’s copper Consume warm food or hot tea. C20.