Green’s Dictionary of Slang

1. (Aus.) the threat of pieces falling from an old, unsafe automobile.

1984

Partridge DSUE (8th edn) 376/2: since ca. 1955.

2. (orig. Aus.) of a woman’s breasts, their falling out of a badly secured or overly low-cut bikini or swimsuit.

1984

Partridge DSUE (8th edn) 376/2: since ca. 1960.