The origin of the lb. abbreviation for pound is in the Latin word "libra", which means both balance scales and also a pound weight. In this case, the full expression was "libra pondo". The second word of that expression gave origin to the word pound.

El origen de la abreviatura lb. (que significa pound) reside en la palabra latina "libra", que significa balanza pero también, peso de una libra. En este último caso, la expresión completa era "libra pondo". La segunda palabra de dicha expresión dio origen a la palabra pound.

(Sent by Patricia Baldonedo from Zaragoza, Spain)