Legend holds that in 1494, an Italian friar named Luca Pacioli was sitting under an apple tree when an apple bounced off his head. In a flash of insight, he invented the “double-entry bookkeeping” system where each entry has a corresponding and opposite entry to a different account. Those entries, called debits and credits, help accountants avoid headaches — if the debits and credits don’t balance, there’s a mistake somewhere. (Some of you may be thinking that was Sir Isaac Newton with the apple inventing gravity, but this is our story and we’re sticking to it.)