Green’s Dictionary of Slang

1. an outdoor lavatory.

1944, 1969

in DARE.

2. a peasant, a country person.

1944, 1969		in DARE.
2024		J. Meades Empty Wigs (t/s) 440: Greenham Common [...] was whiningly moaned about by the boonies and ploucs who lived nearby.

3. a picnic held in the woods.

1964

in Current Sl. (1967) I:4 3/2: Boonie, n. Beer, blanket, and boy party.