Why is Pound represented by lb?

Most of the abbreviations are quite easy to comprehend. kg for kilogram, cm for centimetre, in for inch and the list goes on. But why is it that the imperial unit of mass - Pound is represented as lb. Doesn't quite make any sense right? lb can in no way be read as pound! But still we continue to represent pound as lb without even thinking about it. 

Here's the catch. It comes from ancient Rome. Libra was a unit of mass used then, which was equivalent to 328.9 grams. Libra, in Latin means scales or balance. This abbreviation of Libra is used to represent Pound nowadays.