late 15c. from early Middle Dutch luc, shortening of gheluc "happiness, good fortune," of unknown origin. It has cognates in Dutch geluk, Middle High German g(e)lücke, German Glück "fortune, good luck." Perhaps first borrowed in English as a gambling term. To be down on (one's) luck is from 1832; to be in luck is from 1900; to push (one's) luck is from 1911. Good luck as a salutation to one setting off to do something is from 1805. Expression better luck next time attested from 1802.