French sol

The sol, later called a sou, is the name of a number of different coins, for accounting or payment, dating from Antiquity to today. The name is derived from the solidus. Its longevity of use anchored it in many expressions of the French language.

The solidus is a coin made of 4.5 g of gold, created by emperor Constantine to replace the aureus.

Doing honour to its name, the new currency earns the reputation of unalterability, crossing almost unchanged the decline and fall of the Western Roman Empire, the great invasions and the creation of Germanic kingdoms throughout Europe; not only was it issued in the Byzantine empire until the 11th century under the name of nomisma, but the solidus was imitated by the barbarian kings, particularly the Merovingians, albeit most often in the form of a "third of a sou" (tremissis).

Facing a shortage of gold, a new "stabilization" (as devaluations are often called) is introduced by Charlemagne: from then on the solidus no longer represents 1/12th of the Roman gold pound but 1/20th of the Carolingian silver pound instead. The sou itself is divided into 12 denarii and one denarius is worth 10 asses. But for rare exceptions (saint Louis' "gros"), the denarius will in practice be the only ones in circulation.

Charlemagne's general principle of 12 denarii worth one sol and of twenty sols worth one pound is kept with many variants according to the alloy used and the dual metal gold:silver sometimes used for some issues. In fact only members of the money changers corporation could find their way among the equivalences and the many currencies used in Europe at each period, and therefore were unavoidable for many commercial operations.

The name evolves as does the rest of the language, from Latin to French. Solidus becomes soldus, then solt in the 11th century, then sol in the 12th century. In the 18th century (Ancien Régime) the spelling of sol is adapted to sou so as to be closer to the pronunciation that had previously become the norm for several centuries.

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