History of the French language

The indigenous population of what we call France were the Gauls, a Celtic people with their own Celtic language, Gaulish (of which there are approx. 800 extant written texts). Gaulish would have sounded something like modern-day Welsh. 

When Roman rule expanded to include Gaul in 50 BC, it brought with it the Latin language, which co-existed with Gaulish for several centuries until Vulgar Latin finally prevailed; Gaulish died out by the 500s. 

Vulgar Latin was Latin as spoken by the people. The Latin spoken in France evolved over time and due to exposure to the influence of other languages. 

Around the year 500, tribes who had previously settled lands to the north of Gaul, the Franks, took control of what had been Roman Gaul. Their ruler was Clovis (466-511), who converted to Christianity and was crowned King of the Franks by the Christian church. The language of the Franks was Frankish, a Germanic language. 

Under Frankish rule, in areas with existing Gallo-Roman populations, for several centuries the Frankish language co-existed with Latin. The Latin spoken in Francia morphed into "Roman" (the Gallo-Romance language) becoming Old French by the early 800s. This is the language the Frankish rulers came to adopt as their own. By the 800s, the Frankish language was disappearing, and was extinct in France by the early 1000s. The first ruler of the French not to speak Frankish was Hugh Capet (d. 996). Elsewhere, Frankish developed into modern-day Dutch. 

In the 800s, the incursions of the Normans (Vikings) represented another major linguistic influence. The incoming Norsemen, who spoke the Norse language, came to settle an area to the north now known as Normandy. Within a few generations, the Norseman had adopted French as their language ("Norman French"). By the time agreement was reached with the Normans, in 911, granting them Normandy, their ruler Rollo spoke French. In 1204 Normandy was integrated into the Kingdom of France. Features of the Norse language influenced French. 

Several Old French dialects emerged among people speaking French, differing for example as to how to pronounce the word "yes" - "oc" or "oïl". However, one dialect emerged dominant: Francien. This dialect was spoken in the Île-de-France region in France. The period of Old French, which retained grammatical cases, lasted from 700s to the 1300s; an early written text in Old French was the Oaths of Strasbourg dated 842. The period of Middle French, for example discarding grammatical case, lasted from the 1300s to the 1600s. Modern French emerged in the 1600s, as France became dominant under Louis XIV in the 1600s (the Grand Siecle), and later during the Enlightenment in the 1700s (Siecle des Lumieres). French became the language of international diplomacy, replacing Latin. Later, in the 1800s, the dominance of standardised French was imposed by the Jules Ferry laws, introducing free and universal education.