point the bone, v. — Green’s Dictionary of Slang

point the bone v.

[Aborigine practice of pointing a bone (the ‘death bone’) at one whose death is desired]

(Aus.) to betray a friend and leave them in the lurch; thus bone-pointer n., bone-pointing n.

1951		Cusack & James Come in Spinner (1960) 392: Pointing the bone at me, are you, you old witch?
1957		J. Greenway ‘Aus. Cattle Lingo’ in AS XXXIII:3 164: bone, point the bone at, v. To wish (someone) harm. From the aboriginal practice of pointing a small bone at an enemy to cause his death by magic.
1972		A. Chipper Aussie Swearers Guide 33: The greatest sin against the Australian spirit of mateship is to point the bone at a cobber, i.e. sneak on a friend or leave him in the lurch [Ibid.] 43: Point-the-Bone Merchant. Accuster, often buck-passer.