During the Merovingian period, Frankish had significant influence on the Romance languages which displaced it after these evolved from the Latin language which was introduced into Gaul by the Romans. As a result, many modern French words and placenames, including the country name "France", have a Frankish (i.e. Germanic) origin. France itself is still known by terms meaning the "Frankish Realm" in languages such as German (Frankreich), Dutch (Frankrijk), and Danish (Frankrig). Between the 5th and 9th centuries, the languages spoken by the Salian Franks in Belgium and the Netherlands evolved into Old Dutch (Old Low Franconian), while in Picardy and Île-de-France it was eventually outnumbered and replaced by Old French (the last stage of Latin in its evolution into French) as the dominant language.
The Frankish language as spoken before the Carolingian period is mostly reconstructed from Old French loanwords and from the Old Dutch language as recorded in the 6th to 12th centuries. A notable exception is the Bergakker inscription, which may represent a primary record of 5th-century Frankish.
Germanic philology and German studies have their origins in the first half of 19th century when Romanticism and Romantic thought heavily influenced the lexicon of the linguists and philologists of the time, including pivotal figures such as the Brothers Grimm. As a result, many contemporary linguists tried to incorporate their findings in an already existing historical framework of "stem duchies" and "Altstämme" (lit. "old tribes", i.e. the six Germanic tribes then thought to have formed the "German nation" in the traditional German nationalism of the elites) resulting in a taxonomy which spoke of "Bavarian", "Saxon", "Frisian", "Thuringian", "Swabian" and "Frankish" dialects. While this nomenclature became generally accepted in traditional Germanic philology, it has also been described as "inherently inaccurate" as these ancient ethnic boundaries (as understood in the 19th century) bore little or limited resemblance to the actual or historical linguistic situation of the Germanic languages. Among other problems, this traditional classification of the continental West Germanic dialects can suggest stronger ties between dialects than is linguistically warranted. The Franconian group is a well known example of this, with East Franconian being much more closely related to Bavarian dialects than it is to Dutch, which is traditionally placed in the Low Franconian sub-grouping and with which it was thought to have had a common, tribal origin.
In a modern linguistic context, the language of the early Franks is variously called "Old Frankish" or "Old Franconian" and refers to the language of the Franks prior to the advent of the High German consonant shift, which took place between 600 and 700 CE. After this consonant shift the Frankish dialect diverges, with the dialects which would become modern Dutch not undergoing the consonantal shift, while all others did so to varying degrees. As a result, the distinction between Old Dutch and Old Frankish is largely negligible, with Old Dutch (also called Old Low Franconian) being the term used to differentiate between the affected and non-affected variants following the aforementioned Second Germanic consonant shift.
The Germanic languages are traditionally divided into three groups: West, East and North Germanic. Their exact relation is difficult to determine, and they remained mutually intelligible throughout the Migration Period, rendering some individual varieties difficult to classify.
The language spoken by the Franks was part of the West Germanic language group, which had features from Proto-Germanic in the late Jastorf culture (ca. 1st century BC). The West Germanic group is characterized by a number of phonological and morphological innovations not found in North and East Germanic. The West Germanic varieties of the time are generally split into three dialect groups: Ingvaeonic (North Sea Germanic), Istvaeonic (Weser-Rhine Germanic) and Irminonic (Elbe Germanic). While each had its own distinct characteristics, there certainly must have still been a high degree of mutual intelligibility between these dialects. In fact, it is unclear whether the West Germanic continuum of this time period, or indeed Franconian itself, should still be considered a single language or that it should be considered a collection of similar dialects.
In any case, it appears that the Frankish tribes, or the later Franks, fit primarily into the Istvaeonic dialect group, with certain Ingvaeonic influences towards the northwest (still seen in modern Dutch), and more Irminonic (High German) influences towards the southeast.