Common Brittonic

Common Brittonic (Brythoneg; Brythonek; Predeneg), also known as British, Common Brythonic, or Proto-Brittonic, is an extinct Celtic language spoken in Britain and Brittany.

It is a form of Insular Celtic, descended from Proto-Celtic, a theorized parent language that, by the first half of the first millennium BC, was diverging into separate dialects or languages. Pictish is linked, likely as a sister language or a descendant branch.

Evidence from early and modern Welsh shows that Common Brittonic was significantly influenced by Latin during the Roman period, especially in terms related to the church and Christianity. By the sixth century AD, the languages of the Celtic Britons were rapidly diverging into Neo-Brittonic: Welsh, Cumbric, Cornish, Breton, and possibly the Pictish language.

Over the next three centuries, Brittonic was replaced by Scottish Gaelic in most of Scotland, and by Old English (from which descend Modern English and Scots) throughout most of modern England as well as Scotland south of the Firth of Forth. Cumbric disappeared in the 12th century, and in the far south-west, Cornish probably became extinct in the 18th century, though its use has since been revived. O'Rahilly's historical model suggests a Brittonic language in Ireland before the introduction of the Goidelic languages, but this view has not found wide acceptance. Welsh and Breton are the only daughter languages that have survived fully into the modern day.

Pictish and Pritenic
Pictish, which became extinct around 1000 years ago, was the spoken language of the Picts in Northern Scotland. Despite significant debate as to whether this language was Celtic, items such as geographical and personal names documented in the region gave evidence that this language was most closely aligned with the Brittonic branch of Celtic languages. The question of the extent to which this language was distinguished, and the date of divergence, from the rest of Brittonic, was historically disputed.

Pritenic (also Pretanic and Prittenic) is a term coined in 1955 by Kenneth H. Jackson to describe a hypothetical Roman era (1st to 5th centuries) predecessor to the Pictish language. Jackson saw Pritenic as having diverged from Brittonic around the time of 75–100 AD.

The term Pritenic is controversial. In 2015, linguist Guto Rhys concluded that most proposals that Pictish diverged from Brittonic before c. 500 AD were incorrect, questionable, or of little importance, and that a lack of evidence to distinguish Brittonic and Pictish rendered the term Prittenic "redundant".

Diversification and Neo-Brittonic
Common Brittonic vied with Latin after the Roman conquest of Britain in 43 AD, at least in major settlements. Latin words were widely borrowed by its speakers in the Romanised towns and their descendants, and later from church use.

By 500–550 AD, Common Brittonic had diverged into the Neo-Brittonic dialects: Old Welsh primarily in Wales, Old Cornish in Cornwall, Old Breton in what is now Brittany, Cumbric in Northern England and Southern Scotland, and probably Pictish in Northern Scotland.

The modern forms of Breton and Welsh are the only direct descendants of Common Brittonic to have survived fully into the 21st century. Cornish fell out of use in the 1700s but has since undergone a revival. Cumbric and Pictish are extinct and today spoken only in the form of loanwords in English, Scots, and Scottish Gaelic.

Vowels
The early Common Brittonic vowel inventory is effectively identical to that of Proto-Celtic. and have not developed yet.

By late Common Brittonic, the New Quantity System had occurred, leading to a radical restructuring of the vowel system.

Notes:
 * The central mid vowels and  were allophonic developments of  and, respectively.

Grammar
Through comparative linguistics, it is possible to approximately reconstruct the declension paradigms of Common Brittonic:

First declension
Notes:
 * The dative dual and plural represent the inherited instrumental forms, which replaced the inherited dative dual and plural, from Proto-Celtic toutābom, toutābos.

Second declension
Notes:


 * Neuter 2nd declension stems deviate from the paradigm as such:

Notes:


 * Dual is same as singular
 * All other declensions same as regular 2nd declension paradigm

Place names
Brittonic-derived place names are scattered across Great Britain, with many occurring in the West Country; however, some of these may be pre-Celtic. The best example is perhaps that of each (river) Avon, which comes from the Brittonic aβon[a], "river" (transcribed into Welsh as afon, Cornish avon, Irish and Scottish Gaelic abhainn, Manx awin, Breton aven; the Latin cognate is amnis). When river is preceded by the word, in the modern vein, it is tautological.

Examples of place names derived from the Brittonic languages
Examples are:
 * Avon from abonā = 'river' (cf. Welsh afon, Cornish avon, Breton aven)
 * Britain, cognate with Pritani = (possibly) 'People of the Forms' (cf. Welsh Prydain 'Britain', pryd 'appearance, form, image, resemblance'; Irish cruth 'appearance, shape', Old Irish Cruithin 'Picts')
 * Cheviot from *cev- = 'ridge' and -ed, a noun suffix
 * Dover: as pre-medieval Latin did not distinguish a Spanish-style mixed sound, the phonetic standard way of reading Dubrīs is as . It means 'water(s)' (cognate with old Welsh dwfr, plural phonetically, Cornish dowr, Breton dour, and Irish dobhar, its orthography bh denoting  or  phonetically)
 * Kent from canto- = 'border' (becoming in Welsh cant(el) 'rim, brim', in Breton, kant)
 * Lothian, (Lleuddiniawn in medieval Welsh) from *Lugudũn(iãnon) 'Fort of Lugus'
 * Severn from Sabrīna, perhaps the name of a goddess (modern Welsh, Hafren)
 * Thames from Tamesis = 'dark' (likely cognate with Welsh tywyll 'darkness', Cornish tewal, Breton teñval, Irish teimheal, pointing to a Brittonic approximate word temeselo-)
 * Thanet (headland) from tan-eto- = 'bonfire', 'aflame' (cf. Welsh tân 'fire', Cornish tanses, Old Breton tanet 'aflame')
 * York from Ebur-ākon = 'yew tree stand/group' (cognate with Welsh Efrog, from efwr 'cow parsnip, hogweed' + -og 'abundant in', Breton evor 'alder buckthorn', Scottish Gaelic iubhar 'yew', iùbhrach 'stand/grove of yew trees'; cognate with Évreux in France, Évora in Portugal and Newry, Northern Ireland) via Latin Eburacum > OE Eoforwīc (re-analysed by English speakers as eofor 'boar' with Old English wic appended at the end) > Old Norse Jórvík

Basic words tor, combe, bere, and hele from Brittonic are common in Devon place-names. Tautologous, hybrid word names exist in England, such as:
 * Derwentwater (for Brittonic part see Dover above)
 * Chetwood, (cognate with Welsh coed, Breton koad)
 * Bredon Hill