(of behaviour) acceptable - Australian & New Zealand – informal
As a noun dinkum, recorded from the late 19th century. was an English dialect word meaning hard work, honest toil. It now mainly features as an adjective in various Australian and New Zealand expressions.
RELATED IDIOMS :
done like dinner = done like a dinner
utterly defeated or outwitted - Australian & Canadian informal
1978 - C. Green - The Sun Is Up - I had old Splinters Maloney the fishing inspector knocking on me door wanting to see me licence. Of course I was done like a dinner.
more than someone has had hot dinners
someone's experience of a specified activity or phenomenon is vastly greater than someone else's - British informal
1998 - Odds On - Triplett has been second more times than he's had hot dinners and there must be a question about his bottle. But he has two qualities that will stand him in good stead at the Olympic Club.