Why is finding a penny on the sidewalk good luck?

Answer 1

Well, pennies used to have far more value than they do these days; so much so that both the US and the UK used to mint and distribute a coin called a half-penny (or ha'penny).

So, happening upon a penny centuries ago would've been much like finding a dollar today. And the penny's size (about the equivalent of a modern US quarter) and copper coloration would've made it stand out, especially when new and still shiny. This is probably also what led to the similar term, lucky penny.

And like the expression providing one's two cents, while the coin itself may have been devalued, the saying has stood the test of time. Even though, like Yogi Berra once said, "A nickel ain't worth a dime anymore."