finder

finders keepers (losers weepers) used, often humorously, to assert that whoever finds something by chance is entitled to keep it (and the person who lost it will just have to lament its loss). informal

☞ This expression has been widely used since the early 19th century, although the idea goes back much further and is found in the work of the Roman dramatist Plautus. A variant sometimes heard is findings keepings.