E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The unit of weight (Latin, pondus, weight); also cash to the value of twenty shillings sterling, because in the Carlovingian period the Roman pound (twelve ounces) of pure silver was coined into 240 silver pennies. The
symbols £ and lb. are for libra, the Latin for a pound. (See PENNY for POUND.)