bunce a sudden happening that brings good fortune (as a sudden opportunity to make money)

bunce

: Does anyone know the origin of "Bunce" when referring to receiving payment over and above that which was due?
: Thanks

"BUNCE n. British -- money or profit. A word dating from the 19th century and almost obsolete by the 1960s, except among street traders and the London underworld. In the late 1980s the word was revived by middle-class users such as alternative comedians in search of colourful synonyms in a climate of financial excesses. Bunce may originally have been a corruption of 'bonus.'" "The Dictionary of Contemporary Slang" by Tony Thorne (Pantheon Books, New York, 1990).
"British English: A to Zed" by Norman W. Schur (Harper Perennial, New York, 1987) says the American equivalent is "windfall." And that bunce is informal, "...Originally, just an profit (derived from bonus?) but latterly an unexpected one. It has now gained some currency as a verb, especially in the gerund, buncing, to describe the practice, in retail stores, of sticking new higher-price tags over the original lower-price labels on articles for sale."