Only one ounce...

An ounce (of truth, of intelligence, of….) is one of the UK’s traditional units of weight. The word ounce is from the Latin uncia, meaning a 1/12 part, because the Roman pound was divided into 12 ounces. The Old English word ynce, "inch," meaning 1/12 foot, has the same root.

The symbol oz is from the Old Italian word onza (now spelled oncia) for an ounce. Having 'gone metric' they of course no longer use the oncia but it traditionally it equaled 1/12 libra. Oncia, onza, onça and once are the traditional names for the ounce unit in Romance languages: the Portuguese onça and Spanish onza equal 1/16 libra; the French once equals 1/16 livre)…it may all sound the same but this latter was actually about 2 grams (OK, it's metric!) heavier than the onza/ onça and 3 grams heavier than the oncia! I’m not even going to try to explain all the differences but the Dictionary of Units of Measurement, here (on the site by Russ Rowlett, the Director of the Center for Mathematics and Science Education at University of North Carolina at Chapel Hill) would be very useful if you wanted to dig further.

In actual fact it was the ‘grain’ that was the original unit of weight: the grain was the legal foundation of traditional English weight systems, with various pounds (and hence ounces) being defined as a specified number of grains. Originally the grain was defined in England as the weight of a barleycorn. This made the English grain larger than the corresponding grain units of France and other nations of the Continent (bigger and better? We’ve always known that…) because those units were based on the weight of the smaller wheat grain.

Anyway, back to the ounce: the 'normal' ounce is called the avoirdupois ounce; avoirdupois weights were the common system of weights in all the English-speaking countries. Until quite recently, almost all weights were stated in avoirdupois units, with only precious metals and pharmaceuticals being measured by troy weights (see below). The name of the system comes from the Old French phrase avoir du pois or aveir de pois, "goods of weight," indicating simply that the goods were being sold by weight rather than by volume or per article. The avoirdupois system was introduced in England around 1300, replacing an older commercial system based on a "mercantile pound" (libra mercatoria) It is thought that the avoirdupois pound was originally devised by wool merchants taking as their base the pound of 16 ounces used in Florence, Italy, which at the time was an important buyer of English wool. The avoirdupois weights quickly became the standard weights of trade and commerce.

Then there’s a 2nd traditional unit of mass or weight: the troy ounce, an older English weight system, believed to have been in use since long before the Norman conquest of 1066. The system is believed to be named for the French market town of Troyes, where English merchants traded at least as early as the time of Charlemagne. It is used today only in pharmacy, gold and other precious metals, and jewellery – here you can be led off to pennyweights, drams, scruples etc; in particular, the prices of gold and silver quoted in financial markets are the prices per troy ounce. You think that’s it?...they're all here in Russ' labyrinthine dictionary.

There’s the fluid ounce (unit of liquid volume), an ounce force (a unit of force, equal to the force experienced at the earth's surface by a mass of one ounce), ounce mole (oz mol) a unit of amount of substance (molecular and atomic weights), ounce per gallon (oz/gal) a unit of mass concentration, ounce per square foot (oz/ft2) a traditional unit of density (still used widely in the U.S. for stating the density of coatings and many other applications) and the ounce weight (sounds like the normal ounce but this one is a unit for measuring the density -incorrectly called the "weight".

My favourites, and as yet unmentioned, however, are the ounces that in medieval times were used sometimes as a unit of distance equal to 1/12 yard or 3 inches, or used for a unit of time (TIME!!) equal to 1/12 moment, (this is great stuff! A moment is a medieval unit of time equal to 1/40 hour or 1.5 minutes. The moment was divided into 12 ounces of 7.5 seconds each. Also worth a mention here for another O, the ostent, a medieval name for the time unit now called the minute (just to confuse you -in medieval times a minute was actually equal to 1/10 hour, or 6 modern minutes); the ostent was equal to 8 ounces or 1 modern minute.

Continuing this digression, Gavin Corder has commented on the Ox-man and his goad (a pole in length) but there is also the Oxgang. This was an old English unit of land area equal roughly to 15 acres (6 hectares), or to 1/8 hide; you see how easy it is to become immersed in all this…a hide, very old English unit of land area, was considered the area a farmer could plough with a team of 8 oxen, so an oxgang was the area he could plough with a single ox (of course two oxen could be a span...and a span of an arc/ bridge...OK I'll shut up.) ; dating from perhaps the seventh century, the hide was the amount of land that could be cultivated by a single ploughman and thus the amount of land necessary to support a family. Depending on the type of land/conditions/hills etc this could be as little as 60 acres or as much as 180 acres; the hide was more or less standardized as 120 acres after the Norman conquest of 1066.

S.O.

Just in case you were thinking that this is an out of character post (intelligent, researched, not childish at all...) I add the pussy in this link...
:-)