When writing about Walter's weight, I wondered why “pound” is abbreviated as "lb". Turns out, the Latin word libra means “scales, balances" and it also describes a Roman unit of mass similar to a pound; this is the origin of the abbreviation “lb” or “℔”. "Pound" itself it comes from the Latin word pendere, meaning “to weigh”.
Interesting side note: the plural form of “lb” is the same: "lb", with no“s” at the end. Units of measure do not have plural forms (I drove 100Km, not 100Kms; I bought 100g, not 100gs).