Green’s Dictionary of Slang

plongkas n.

also pluncas

[echoic plonk, the noise it makes hitting a plate or the floor]

(W.I.)

1. a heavy cake or dumpling.

1943

cited in Cassidy & LePage Dict. Jam. Eng. (1980).

2. a heavy shoe.

1943

cited in Cassidy & LePage Dict. Jam. Eng. (1980).