If someone tells you she doesn’t know a person from Adam, she’s telling you she doesn’t know him (or her, of course). More liberally, it’s possible that she’s heard of him or has even met him virtually; she just has no first-hand knowledge of him and wouldn’t recognize him in a crowd.
The Adam in this axiom is, of course, the first-created man, introduced to us — and into the world — in the Book of Genesis. In the expression, the comparison is to this historical Adam, who predates us to such a degree that no one can say for certain what he looked like, even though he’s familiar to us by reputation. In this same sense, being the archetypal human being, Adam represents all mankind, and she simply can’t distinguish the person being discussed from anyone else amongst the 9 billion of us traipsing about the Earth today.
A variant to this expression has perhaps passed into history, though the sentimental amongst us can still listen for Nick, the new owner of Martini’s tavern, tell the never-was George Bailey,“I don’t know you from Adam’s off-ox,” in the Christmas classic “It’s a Wonderful Life.” The off-ox is the one behind the first ox relative to the driver, and thus, is least visible — and thus difficult to discern from any other ox.
“Then the Lord God formed a man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being.”
— Genesis 2:7, Scripture from The Holy Bible, New International Version
Many of our most popular idioms that endure to this day stem from the Good Book – or rather, the 66 great books that make up The Holy Bible. Somehow – miraculously – dozens of these colloquialisms from millennia ago have survived multiple translations and innumerable cultures through time to remain in common use today. Idioms From Heaven collects, dissects, and shares this pithy wisdom to edify and educate all.