Green’s Dictionary of Slang

1. a rich fool [they are surrounded by money].

1926

Wood & Goddard Dict. Amer. Sl. 15: doughnut. Money all around, nothing in the middle; a rich fool.

2. (also donut) a fool, irrespective of income [? the emptiness at the doughnut’s centre].

2000		J.J. Connolly Layer Cake 215: The old bill, not being stupid like some doughnuts think, always protect their source.
2009		J. Joso Soothing Music for Stray Cats 140: There I was stuck with a total doughnut.
2011		Guardian 8 Aug. 🌐 In 2006 he wrote an article for the Guardian calling him a ‘donut’, for blaming knife crime on the influence of rap.
2015		thewire.co.uk Oct. 🌐 This was after Wiley dissed former ally God’s Gift live on air, calling him a ‘donut’, which allegedly resulted in God’s Gift and crew gatecrashing the station to beat up Wiley.
2020		G. Krauze What They Was 250: Let’s face it, if you get caught or you fuck up and get sentenced to community service you’re a bit of a doughnut.