For many centuries, Latin was the only written language over an area, “greater” Francia, that came to stretch from Norway to Portugal and from Iceland to Catholic parts of the Ukraine. A Swede like Karl von Linné would be known by a Latinized name as Carolus Linnaeus, and an Italian like Christoforo Columbo as Christopherus Columbus.
One consequence of the dominance of Latin was the universal use of the Latin alphabet, and the borrowing of Latin vocabuary for vernacular languages from Norwegian to Hungarian. Islâm was not tolerated in Mediaeval Francia, except in unusual circumstances, mainly in Spain and Sicily (the arabian numbers we now use today were adopted much later!). The alphabet that had been developed to write Gothic disappeared with its language. The old Runic alphabet also largely disappeared with the Christianization of Germany and Scandinavia.
The use of the Latin alphabet in Francia often goes along with languages, the Romance languages, that are themselves descended from Latin, like Italian, French, Spanish, Portuguese, and Romanian.
On the other hand, Francia was the result of the West Roman Empire collapsing under the inroads of germanic tribes and then of a new identity being formulated by the Germanic Franks. Meanwhile, the language family that was displaced by the Romans in Gaul and Angles and Saxons in Britain persists in the “Celtic Fringe” of Ireland, Scotland, and Wales, including Brittany, which was actually colonized with refugees from Celtic Britain. Welsh betrays its heritage as the language of Roman Britain with Latin days of the week and other borrowings.
In the East, the Slavic languages represent another boundary. After the initial migration of Slavic speakers that pushed Germans behind the Elbe they replaced large areas of indigenous languages in the Balkans. Between the northern and southern Slavs, however, is a Romanic speaking remnant in the Balkans, Romania.
The Hungarians, who were the only steppe people to first invade Europe but then settled down and even retained their linguistic identity, despite their country often being called after the earlier and unrelated Huns.
The only other languages in Francia related to Hungarian are Finnish and Estonian, which are probably at the western end of a very ancient distribution of the Uralic languages. The language that has the best claim to being the autochthonous language of Francia is Basque, which has no established affinities with any other language in the world. Off the map is another little bit of Francia, Malta, where a language is spoke, Maltese, that is descended from Arabic and so unrelated to other modern languages in Francia. This is a remnant of the Aghlabid conquest of Sicily, although now the Maltese have long been Catholic, and the language is written, of course, in the Latin alphabet.