If something is proverbial, it is from a story or saying that is well known. The proverbial Fountain of Youth will make you forever young. The proverbial Pie in the Sky is where your wildest dreams come true.
Proverb is the root of proverbial, and proverb comes from the Latin word proverbium, meaning “a common saying.” Proverbs are little stories or expressions that usually teach a lesson. You may have heard of the proverbial pot of gold at the end of the rainbow? Better to seek the proverbial penny saved, because that’s a penny earned. And the proverbial gift horse? Don’t look him in the mouth.