Why is pounds written as pounds?

Answer 1

Lb is an abbreviation of the Latin word for pound. The original Latin word for the pound weight was libra pondo.

The Latin word libra means 'balances, scales' (as in the astrological sign for the constellation Libra, which can be described as looking like a set of balance scales). The word pondus, meaning weight, is the original Latin for the English word 'pound.' So libra pondo meant 'a balance scale weight (of a Roman pound)'. A Roman pound weighed about 327 grams. [The British pound became standardised at about 1/3rd heavier than the ancient Roman pound]

In time libra pondo became shortened to just libra, i.e. a quick way of saying 'libra pondo.' Then libra was abbreviated to lb, still meaning pound or pounds. Lbs is the logical English plural of lb, but either lb or lbs can be used.