kill two birds with one stone

Example: “I'll visit Grandma and pick up the groceries on the way, killing two birds with one stone.”

Origin: Its earliest known appearance in English is in Bishop John Bramhall's A Defence of True Liberty (1655), part of his long quarrel with the philosopher Thomas Hobbes over free will: "T. H. thinks to kill two birds with one stone, and satisfy two arguments with one answer." Hobbes reprinted the passage in his reply, The Questions concerning Liberty, Necessity, and Chance (1656), the date most dictionaries give. The underlying image of an efficient double gain is much older and its exact source is unsettled. One theory reaches for Greek mythology, crediting Daedalus with killing two birds with a single stone to gather feathers for the wings he built to escape Crete. A second points to a considerably plainer English proverb from John Heywood's 1546 collection, "I will learn to stop two gaps with one bush" — the same principle of one action solving two problems, applied to fence repair rather than birds. Similar efficiency proverbs existed in Latin well before either, suggesting the core idea long predates any single credited source.