The word inch comes from the Latin word uncia, which means 1/12 (in this case, 1/12 of a foot).

In French, the word for inch is pouce, which means "thumb." This is where the modern Arabic word بوصة comes from. In an attempt to come up with a less bastardized word for "inch," some people translated the French word "pouce" to عقدة in the sense of عقدة الاصبع, which refers to one phalanx of the thumb.

Needless to say, this coinage has not been successful.