Surplus, hidden or additional quantities of something, especially if secretly concealed until a key moment for advantageous gain or cheating
Origin: random hyper-localised sayings, Rothwell, Leeds 1990s.
Person A: Yay!, Iรขยยve won this game of Monopoly.
Person B: Ahh, no, because I have this COOPER MONEY!
or
I thought we'd run out of crisps, but I found all these cooper crisps in the other cupboard.
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