More language stuff I love (from Huffpost): 

We use the abbreviations “tbsp” for tablespoon, “ft” for foot, “yd” for yard. Why “lb” for pound?
Because the abbreviation comes from the Latin word “libra.”
In Roman times, the word libra referred to balance or scales. It was also part of a unit of measurement ― libra pondo, which has been translated as “pound weight” or “a pound by weight.” So the shorthand libra, or “lb,” referred to a pound by weight. “Pondo” becomes “pound.”

The earliest known uses of “libra” or “lb” for pound in the English language supposedly appear in the 14th century.