To make every possible effort to find something or achieve a goal, examining all possibilities thoroughly.
This phrase dates back to ancient Greece and the legend of the Persian general Mardonius, who supposedly hid treasure under stones after his defeat at Plataea in 479 BCE. The Oracle at Delphi advised treasure seekers to 'leave no stone unturned' to find it. The expression entered English literature in the mid-16th century and has remained virtually unchanged in form and meaning.
What's remarkable is how this 2,500-year-old phrase about literal stone-turning has become our go-to metaphor for thoroughness. It's a testament to how physical actions can become powerful mental concepts - the image of methodically lifting every stone perfectly captures the exhaustive nature of a complete search.
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