Dialects of Latin
Throughout Roman history, there was regional variation in the Latin language. In certain regions, terms or morphological features from pre-Roman substrate languages were borrowed into the local dialects. For instance, the dialect of Gaul borrowed terms from their native Gaulish language, which was spoken by the Gauls, a Celtic people. Regional dialects were often perceived as inferior to the prestige "Roman" dialect, which—in the view of some authors—may have constituted a genuine style of speech common to the city of Rome. However, other authors perceived their ideal "Roman dialect" as an artificial, prescribed standard of "correct" speech that did not necessarily reflect the vernacular of any given region.
Gaulish
Influence of substrate languages
There are numerous inscriptions from Gaul written in a mixed dialect of Latin and Gaulish, with both languages borrowing heavily from the other. One inscription from Autun reads geneta vis cara, containing the Gaulish word geneta but the Latin terms vis and cara. Another text, also from Autun, reads nata vimpi pota vim, containing only one Gaulish term: vimpi. Other texts appear more as Latinized Gaulish than as Gallicized Latin: the Lezoux Plate is largely Gaulish, although it contains the Latin loanwords vero and curri. The Lex Salica, a Frankish legal text created around 500 CE, provides further attestation of Gallo-Roman words derived from Celtic sources. The text contains terms such as segusium or vassus, from Proto-Celtic *segūsios and *wassos respectively. Adams suggests that the Gaulish language likely imposed the greatest influence on the local dialects of Latin shortly after the Roman conquest, as native Gaulish speakers aimed to learn Latin as a second language. Adams further argues that the Gallic influence likely waned over time, as the decline of the Gaulish language ensured that the newer speakers of Gallo-Latin acquired their dialects more distant from the influence of native Gaulish speakers. Gaulish texts from La Graufesenque contain the first declension nominative plural ending -as instead of the standard ending -ae, such as in the terms licuias and pannas. Adams argues that this may derive from the original Gaulish nominative plural ending -as and may have been reinforced by the presence of the ending in the nominative plural in other dialects of Latin.Gallo-Latin texts from La Graufesenque dated to the 1st-century CE contain the Latin term canastrum, a dialectal variant of canistrum, both of which derive from Ancient Greek κάναστρον. The Gaulish term is closer to the original Greek term, leading Adams to suggest that the Gauls directly borrowed the word from Greek colonies rather than from native Latin speakers. Furthermore, the given term may have possessed a distinct meaning from the standard Latin term: the Gaulish term is used to describe an earthenware vessel, a meaning shared between this term and the original Greek word, although the standard Classical Latin form is exclusively attested as referring to wicker wood vessels and rarely gold or silver vessels.
Within Gallo-Roman naming conventions, it was common to adopt a traditionally Gaulish name as a cognomen: the female name Livia Divogena utilizes the Latin nomen Livia and the Gaulish cognomen Divogena and the male name Sex Iuenti Senoviri Dubnotali f utilizes the Latin praenomen Sextus and the Gallic names Senoviri and Dubnotali. Gaulish personal names developed into Roman gentile names: the Gallo-Roman man S. Matucenius Frontinus and his daughter, Matucenia Placida, borrowed their gentile name—Matucenius—from the Gaulish name Matucenius. In other circumstances, Gaulish patronymics developed into Roman gentile names: the Gallo-Roman woman Carantia Aelia adopted her name from her the cognomen of her father—Medillio Caranto. Latin influence appears even in circumstances in which names were transcribed according to traditional Gallic naming formula: the phrase Sacrillos Carati contains exclusively Gaulish names, although it shows that Latinized genitive singular ending -i. Another inscription reading Frontu Tarbetisnios contains the Latin cognomen Frontinus used as an individual name, although the overall inscription conforms more to Gaulish styles of naming formula than Roman.
Gallo-Romans also created new names by Latinizing preexisting names, possibly—in some circumstances—by calquing Gaulish names into Latin. One inscription attests to a Gallo-Roman woman with the Latin name Ursula, a name which derives from the Latin word ursa, meaning 'bear'. This woman was the daughter of another woman named Artula, a Gaulish name which likely derives from the Gaulish word for bear: *arto-. Stüber argues that the daughter was likely named after her mother, and the Gaulish name was calqued into a Latin equivalent. Other examples, such as the Roman names Primus, Primigenius, Primullus, which may have emerged in Roman Gaul as calques of the Gaulish names Cintus, Cintugenus, and Cintullus, all of which derive from *kintu-. The classicist Andreas Gavrielatos argues that the appearance of numeral names in Gallo-Roman inscriptions suggests that the custom of Gaulish numeral names was preserved, although the Gaulish names were replaced with Latin equivalents. Gavrielatos cites the example of a Gallo-Roman man with the Gaulish numeral name Cintullus, who gave his son the Roman name Tertius and his daughter the Roman name Quintia. Likewise, his son married a woman with the Latin numeral name Secunda, who was herself the daughter of Toutilli, a man with a Roman name. Elements of Gaulish culture were preserved in Gallo-Roman names, such as the names Epponus or Epidius, which derive from the name of the Gallo-Roman goddess Epona, whose name ultimately derived from a Celtic root.
Fathers with Gaulish names often granted their children Roman names: the Gallo-Roman man Litumari provided his son with the Latin name Silvanus and the Gaulish man Excingi named his son Albanus. However, other inscriptions attest to individuals with Roman names granting their children Gaulish names: the Gallo-Roman man Gemellus provided his son with the Gaulish name Divixtos, which utilizes the Gaulish nominative singular ending -os instead of the Latin ending -us. The linguist Karin Stüber suggested that, at least for a certain period of time, both Gaulish and Roman names were used frequently amongst the Gallo-Roman population.
Phonology
During the transition from Classical Latin to Proto-Western-Romance the long and short vowels merged into close, and the long vowel and the short merged into close. This phonological development can be observed in Gaulish inscriptions that confuse the spellings and, such as ficit for fecit or menus for minus, and spellings that confuse and. Research by the Hungarian linguist Adamik Béla suggested that, although a minority of inscriptions dated to the first three centuries CE demonstrate conflation of the and graphemes, such confusion was more common in the Gaulish provinces of Aquitania, Lugdunensis, and Narbonensis. In contrast, the Gaulish province of Belgica showed significantly fewer examples of such orthographic confusion. However, from the years 301-500 CE, the rates of vowel confusion across all Gaulish provinces dramatically increase, with Belgica emerging as the province displaying the most instances of such vowel conflation. Belgica and Narbonensis also reveal the least examples of confusion between and during the first three centuries CE, although—like in all Gaulish provinces—it increased over time.Linguist Joseph Barbarino collected data regarding the potential confusion of the graphemes and in initial, intervocalic, postconsonantal position or in verb endings. His data revealed that—from the 4th to the 5th century, within the provinces of Lugdunensis and Narbonensis—there were 593 correct usages of the grapheme compared to only 19 errors. Inscriptions from the same provinces during the 6th-7th centuries reveal 164 cases of correct uses of compared to only 5 inaccurate uses. Collectively, this data reveals little evidence of a merger between and, a phenomenon that occurred throughout the Romance world, including Gallo-Romance. This may indicate that the merger occurred at a slower rate within Gallo-Romance than other branches of the Romanic languages. However, Barbarino notes that a higher percentage of intervocalic errors were founded in inscriptions from Lugdunensis, leading him to conclude that the merger was either underway or completed within the region by the 5th-century.
Evidence from La Graufesenque reveals the dialectal form paraxidi, a variant of paropsidi, and inbrax, an uncertain form perhaps related to Latin bractea. These terms may have preserved an ancient feature of Gaulish orthography: the velar spirant, a phoneme within the Gaulish language, was transcribing utilizing the Greek letter χ. This velar spirant appeared in the first letter of the consonant clusters ps, pt, and kt. Adams suggests that further evidence for the presence of the velar spirant in Gaulish Latin appears in surviving French words. For instance, the French term caisse may be explained as a derivation from a Gallicized variant *caxsa, itself from capsa. Another feature of the Gaulish language that may have been preserved into the Gallo-Roman dialect was the merger of long and into a close vowel represented orthographically as, a feature attested in Gallic-Latin by the frequent misspellings of the Latin term acetabulum as acitabulum. Gallo-Latin inscriptions sometimes a unique letter referred to as the tau Gallicum that likely represented a dental phoneme.
Consentius, a 5th-century Latin grammarian, claims that a certain "iotacism" afflicts the dialects of provincial Romans. Consentius claims that Gauls pronounce the letter "more richly ", citing the example of the in the term ite, which the Gauls supposedly pronounce which a "richer sound" between and. It is possible that Consentius was referring to the shift from long to short and from short to, a development which occurred in the Romance languages. He contrasts the Gaulish dialect with the Greek dialect, which he believes to favor a "thinner" pronunciation, leading to the Greeks pronouncing the term ius in such a manner that it becomes disyllabic. He further contrasts both accents with the ideal, although possibly not typical, Roman pronunciation, in which was pronounced in a "thin" manner when placed at the beginning of words, a "richer" sound at the end of words, and the in-between sound when placed in the middle of words. Consentius appears to be prescribing "correct" language as opposed to describing dialectical features of Latin: he explicitly advises his readership to avoid barbarisms by ensuring their speech is not "richer or thinner than the theory of Roman language demands". This passage utilizes the term ratio, which Quintilian includes within his criteria for proper speech: "Reason, Antiquity, Authority, and Usage ".