These words must seem weird to
those who follow the metric system, so a bit of history might
help explain. The Latin word Libra is abbreviated to 'lb'. Libra
is widely known as the astrological sign for balance, but it was
also part of the Roman unit of weight, libra pond, which
translates to “pound weight." Britain derived pound from that
expression as its unit of measurement and also as a term for its
currency because centuries ago, a pound in money was considered
equal to the value of a pound of silver.
Ounces - The Spanish ounce (Onza) was 1⁄16 of a pound. It is a
unit of mass used in most British systems of measurement. It is
most pervasive in the retail sale of groceries in the United
States, but is also used in many other matters of domestic and
international trade between imperial or customary measurement
driven countries.