LB is actually the abbreviation for Libra. And for any one out there who knows their astrological signs, you know that Libra is represented as a scale. Although the gods used the scale to weigh the souls of people against good versus evil, people used scales to weigh materials such as gold and silver against other "worthless" materials (lead, iron, etc.).
The British pound (money) uses a letter that looks like an L with a line through it (£), once again, an abbreviation for Libra.
There are three different pounds refering to weight, although the troy pound and the apothecaries' pound are equal. We use the avoirdupois pound, which is 16 ounces, which isn't the same as the Roman Libra of 327.45 grams... our pound is equal to 453 grams.
Okay, I'm probably confusing you will all these libras, pounds, ounces, and grams, so I'll stop.
I would recommend, though, that we start using the metric system more, so we can be in line with the rest of the world.