Dob
Tell on someone.
Person 1"Who told Mum?"
Person 2"Wasn't me. I'm no dobber."
You'll also hear
Dobbera snitch
Dob inreport someone
Where it's from
Probably from British dialect dob, to put down or throw. Recorded in Australia from the 1950s.

Something wrong or missing? Suggest a fix
While you're here
No. Starting with yeah makes it sound a bit more friendly.
Afternoon. Used heaps by basically everyone.
Genuine, true, no word of a lie. Also a question: "Fair dinkum?"
Petrol station. Also where you buy a pie, milk and a bag of ice at 11pm.
Toilet. Traditionally an outhouse down the back of the yard, now any toilet at all.
Used to explain something that's chaotic or a complete mess.