inch

The ancient Romans used a system of weights and measures based on units divided into 12 parts. Thus the Latin uncia, meaning “a 12th part,” designated the 12th part of a foot. From this is derived Old English ince or ynce and modern English inch. The Roman pound was also divided into 12 parts, similarly designated by the word uncia. In this sense uncia followed a different path and became Middle English unce or ounce, which was the 12th part of a pound in the troy system. In the avoirdupois system, which is more widely used, the pound is larger and equals 16 ounces. The English noun inch dates to before the 12th century; the verb meaning “to move very slowly” does not appear until around 1600.