Most measurements in the English language have pretty straightforward abbreviations ― “tbsp” for tablespoon, “qt” for quart, “yd” for yard and so on. So why, then, do we use “lb” to refer to pound?
The answer goes back to ancient Rome. “Lb” is an abbreviation of the Latin word libra. Astrology buffs will know that Libra is the seventh sign of the zodiac and is symbolized by an image of scales.
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.
The “pondo” part of that ancient Roman measurement, meanwhile, is the origin of the word “pound” in English.
Although the word “pound” evokes a measurement of weight for Americans, British people are more likely to associate it with their currency ― the pound sterling, aka the pound. This is because its original value was equivalent to a pound of silver.
Interestingly, the symbol of a British pound (£) is also related to the word libra, as it is an ornate form of the capital letter L. The Italian lira ― and its similar symbol ― also derives from libra. And the pound sign (#) is related to libra pondo and the way medieval scribes wrote the abbreviation “lb.”
A related term with an unintuitive shorthand is ounce, which also dates back to the Roman period. Ounce is related to the Latin word “uncia,” which referred to one-twelfth of something as a unit of weight, length and volume. We get the English words inch and ounce from “uncia” because in ancient Rome, a pound was actually 12 ounces, rather than 16.
The word “uncia” became “ynce” in Old English, which eventually turned into “inch.” “Ounce” came into English by way of the French “unce” or “once,” which also derived from “uncia.” The abbreviation “oz,” however, stems from medieval Italians, who used “onza.”