mint of money, make a

mint of money, make a

Strike it rich; earn a huge profit. The mint in question here is the place where money is manufactured under government auspices, and by extension it betokens a vast amount of cash. “Mint of money” has been so used since the sixteenth century, but the idea of “making” it dates only from the nineteenth century, when large sums began to be acquired less from inherited wealth than from business enterprise.
See also: make, mint, of