Green’s Dictionary of Slang

twonk n.

a fool.

1981		J. Sullivan ‘Big Brother’ Only Fools and Horses [TV script] You dozy little twonk Rodney, this is prima-facie evidence ain’t it, eh?
2023		R. Milward Man-Eating Typewriter 20: [I]f only those twonks could vada how hideous this omi is beneath the schmutta!