Question: What was the version of the language where the last name Sylvester originates, used in the era of the king that united the tribes in the 9th century, later called?

Passages:
The migration-period peoples who later coalesced into a "German" ethnicity were the Germanic tribes of the Saxons, Franci, Thuringii, Alamanni and Bavarii. These five tribes, sometimes with inclusion of the Frisians, are considered as the major groups to take part in the formation of the Germans. The varieties of the German language are still divided up into these groups. Linguists distinguish low Saxon, Franconian, Bavarian, Thuringian and Alemannic varieties in modern German. By the 9th century, the large tribes which lived on the territory of modern Germany had been united under the rule of the Frankish king Charlemagne, known in German as Karl der Große. Much of what is now Eastern Germany became Slavonic-speaking (Sorbs and Veleti), after these areas were vacated by Germanic tribes (Vandals, Lombards, Burgundians and Suebi amongst others) which had migrated into the former areas of the Roman Empire. Sylvester is a name derived from the Latin adjective silvestris meaning ``wooded ''or`` wild'', which derives from the noun silva meaning ``woodland ''. Classical Latin spells this with i. In Classical Latin y represented a separate sound distinct from i, not a native Latin sound but one used in transcriptions of foreign words. After the Classical period y came to be pronounced as i. Spellings with Sylv - in place of Silv - date from after the Classical period. Charlemagne's court in Aachen was the centre of the cultural revival sometimes referred to as the "Carolingian Renaissance". Literacy increased, as did development in the arts, architecture and jurisprudence, as well as liturgical and scriptural studies. The English monk Alcuin (d. 804) was invited to Aachen and brought the education available in the monasteries of Northumbria. Charlemagne's chancery—or writing office—made use of a new script today known as Carolingian minuscule,[M] allowing a common writing style that advanced communication across much of Europe. Charlemagne sponsored changes in church liturgy, imposing the Roman form of church service on his domains, as well as the Gregorian chant in liturgical music for the churches. An important activity for scholars during this period was the copying, correcting, and dissemination of basic works on religious and secular topics, with the aim of encouraging learning. New works on religious topics and schoolbooks were also produced. Grammarians of the period modified the Latin language, changing it from the Classical Latin of the Roman Empire into a more flexible form to fit the needs of the church and government. By the reign of Charlemagne, the language had so diverged from the classical that it was later called Medieval Latin.

Supporting sentences:
By the 9th century, the large tribes which lived on the territory of modern Germany had been united under the rule of the Frankish king Charlemagne, known in German as Karl der Große. Sylvester is a name derived from the Latin adjective silvestris meaning ``wooded ''or`` wild'', which derives from the noun silva meaning ``woodland ''. By the reign of Charlemagne, the language had so diverged from the classical that it was later called Medieval Latin.