Gresham's Law
A monetary principle stating that "bad money drives out good". If there are two forms of commodity money in circulation — which are accepted by law as having similar face value — the more valuable commodity will gradually disappear from circulation. Seen more often in earlier contexts of silver or even copper coins.
Origin
Named in 1857 by economist Henry Dunning Macleod after Sir Thomas Gresham (1519–1579), English financier to Queen Elizabeth I, who elucidated the principle in 1558. However, Gresham was not the first to recognize it—the concept was thoroughly defined in Renaissance Europe by Nicolaus Copernicus and known centuries earlier in classical Antiquity, the Near East, and China. The law arose from England's Great Debasement (1544–1551) under Henry VIII and Edward VI, when the crown reduced silver content in coins from 92.5% to 25% by 1551. If two coins have similar face value but different intrinsic metal value, the more valuable coin disappears from circulation as people hoard it.