A piece of wood was split down the middle, giving two parts—the stock and the foil. A value was marked—tallied—on the stock and was also marked on the foil, which acted like a receipt. If I lent some money to the Bank of England I would be given a stock with a notch indicating the amount—which explains the origins of the words “stockholder” and “stockbroker”—while the bank kept the foil, which had a matching notch.

— Here's looking at Euclid by Alex Bellos