In British slang, profit or money gained dishonestly or as a perquisite beyond one's regular pay.
From obsolete English bunce, possibly related to bounce or bulge. British vernacular from 19th-20th centuries, particularly associated with working-class slang.
Every profession develops secret slang for money made 'under the table'—'bunce' reveals Victorian and Edwardian workers' humor about stretching honest work into extra income!
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