The Cumbric personal names Gospatrick, Gososwald and Gosmungo meaning 'servant of St...' (Welsh, Cornish, Breton gwas 'servant, boy') and the Galloway dialect word gossock 'short, dark haired inhabitant of Wigtownshire' (W. gwasog 'a servant') apparently show that the Cumbric equivalent of Welsh and Cornish gwas & B gwaz 'servant' was *gos. Jackson suggests that it may be a survival of the original Proto-Celtic form of the word in –o- (i.e. *uɸo-sto).
This idea is disputed by the Dictionary of the Scots Language; and the occurrence in Gospatrick's Writ of the word wassenas 'dependants', thought to be from the same word gwas, is evidence against Jackson's theory. Koch notes that the alternation between gwa- and go- is common among the Brittonic languages and does not amount to a systematic sound change in any of them.
Thomas Clancy opined that the royal feminine personal name in Life of Kentigern, Languoreth, demonstrates the presence of /gw/ Cumbric.
It is noteworthy that the toponym Brenkibeth in Cumberland (now Burntippet; possibly bryn, "hill" + gwyped, "gnats") may display this syllable anglicized as -k-. The name, however, may not be Brittonic at all, and instead be of Scandinavian origin.
In the Book of Aneirin, a poem entitled "Peis Dinogat" (possibly set in the Lake District of Cumbria), contains a usage of the word penn "head" (attached to the names of several animals hunted by the protagonist), that is unique in medieval Welsh literature and may, according to Koch, reflect Cumbric influence ("[r]eferring to a single animal in this way is otherwise found only in Breton, and we have no evidence that the construction ever had any currency in the present-day Wales"). The relevant lines are:
Translated as:
The form derwennydd however, is at odds with the absence of the ending -ydd noted below.
It is to be noted, however, that such semantics are probably archaisms, and rather than being features diagnostic of linguistic distinctiveness, are more likely to be legacies of features once common to all Brittonic speech.
The modern Brittonic languages have different forms of the definite article: Welsh yr, -'r, y, Cornish an, and Breton an, ar, al. These are all taken to derive from an unstressed form of the Common Brittonic demonstrative *sindos, altered by assimilation (compare the Gaelic articles). Throughout Old Welsh the article is ir (or -r after a vowel), but there is evidence in Cumbric for an article in -n alongside one in -r. Note the following:
Of all the names of possible Cumbric derivation, few are more certain than Carlisle and Derwent which can be directly traced back to their Romano-British recorded forms Luguvalium and Derventio.
The modern and medieval forms of Carlisle (Luel c1050, Cardeol 1092, Karlioli c1100 (in the Medieval Latin genitive case), Cærleoil 1130) and Derwent (Deorwentan stream c890 (Old English), Derewent) suggest derivations from Br *Luguvaljon and *Derwentjō. But the Welsh forms Caerliwelydd and Derwennydd are derived from alternative forms *Luguvalijon, *Derwentijō which gave the -ydd ending. This appears to show a divergence between Cumbric and Welsh at a relatively early date.
If this was an early dialectal variation, it can't be applied as a universal sound law, as the equivalent of W mynydd 'mountain' occurs in a number of Cumbric names with the spirant intact: E.g. Mindrum (Minethrum 1050) from 'mountain ridge' (Welsh mynydd trum). It might also be noted that Medieval Welsh forms of Caerliwelydd and Derwennydd both occur in poems of supposed Cumbrian origin whose rhyme and metre would be disrupted if the ending were absent.
Of additional relevance is that Guto Rhys demonstrated "some robust proof" of the presence of the -ydd ending in the closely aligned Pictish language.
One particularly distinctive element of Cumbric is the repeated use of the element Gos- or Cos- (W. gwas 'boy, lad; servant, attendant') in personal names, followed by the name of a saint. The practice is reminiscent of Gaelic names such as Maol Choluim "Malcolm" and Gille Crìosd "Gilchrist", which have Scottish Gaelic maol (Old Irish máel 'bald, tonsured; servant') and gille ('servant, lad', < Old Irish gilla 'a youth').
The most well-known example of this Cumbric naming practice is Gospatric, which occurs as the name of several notable Anglo-Scottish noblemen in the 11th and 12th centuries. Other examples, standardised from original sources, include Gosmungo (Saint Mungo), Gososwald (Oswald of Northumbria) and Goscuthbert (Cuthbert).
It is impossible to give an exact date of the extinction of Cumbric. However, there are some pointers which may give a reasonably accurate estimate. In the mid-11th century, some landowners still bore what appear to be Cumbric names. Examples of such landowners are Dunegal (Dyfnwal), lord of Strathnith or Nithsdale; Moryn (Morien), lord of Cardew and Cumdivock near Carlisle; and Eilifr (Eliffer), lord of Penrith.
There is a village near Carlisle called Cumwhitton (earlier Cumquinton). This appears to contain the Norman name Quinton, affixed to a cognate of the Welsh cwm, meaning valley. There were no Normans in this area until 1069 at the earliest.
In the Battle of the Standard in 1138, the Cumbrians are noted as a separate ethnic group. Given that their material culture was very similar to their Gaelic and Anglian neighbours, it is arguable that what set them apart was still their language. Also the castle at Castle Carrock – Castell Caerog – dates from around 1160–1170. Barmulloch, earlier Badermonoc (Cumbric "monk's dwelling"), was given to the church by Malcolm IV of Scotland between 1153 and 1165.
A more controversial point is the surname Wallace. It means "Welshman". It is possible that all the Wallaces in the Clyde area were medieval immigrants from Wales, but given that the term was also used for local Cumbric-speaking Strathclyde Welsh, it seems equally, if not more, likely that the surname refers to people who were seen as being "Welsh" due to their Cumbric language.
Surnames in Scotland were not inherited before 1200 and not regularly until 1400. Sir William Wallace (known in Gaelic as Uilleam Breatnach – namely William the Briton or Welshman) came from the Renfrew area – itself a Cumbric name. Wallace slew the sheriff of Lanark (also a Cumbric name) in 1297. Even if he had inherited the surname from his father, it is possible that the family spoke Cumbric within memory in order to be thus named.
There are also some historical pointers to a continuing separate ethnic identity. Prior to being crowned king of Scotland in 1124, David I was invested with the title Prince of the Cumbrians. William the Lion between 1173 and 1180 made an address to his subjects, identifying the Cumbrians as a separate group. This does not prove that any of them still spoke Cumbric at this time.
The legal documents in the Lanercost Cartulary, dating from the late 12th century, show witnesses with Norman French or English names, and no obvious Cumbric names. Though these people represent the upper classes, it seems significant that by the late 12th century in the Lanercost area, Cumbric is not obvious in these personal names. In 1262 in Peebles, jurymen in a legal dispute over peat cutting also have names which mostly appear Norman French or English, but possible exceptions are Gauri Pluchan, Cokin Smith and Robert Gladhoc, where Gladhoc has the look of an adjectival noun similar to Welsh "gwladog" = "countryman". In the charters of Wetherall Priory near Carlisle there is a monk called Robert Minnoc who appears as a witness to 8 charters dating from around 1260. His name is variously spelled Minnoc/Minot/Mynoc and it is tempting to see an equivalent of the Welsh "mynach" – "Robert the Monk" here.
Given that in other areas which have given up speaking Celtic languages, the upper classes have generally become Anglicised before the peasantry, it is not implausible that the peasantry continued to speak Cumbric for at least a little while after. Around 1200 there is a list of the names of men living in the area of Peebles. Amongst them are Cumbric names such as Gospatrick: servant or follower of Saint Patrick, Gosmungo: servant of Saint Mungo, Guososwald: servant of Oswald of Northumbria and Goscubrycht: servant of Cuthbert. Two of the saints – Oswald and Cuthbert — are from Northumbria showing influence on Cumbric not found in Welsh.
In 1305 Edward I of England prohibited the Leges inter Brettos et Scottos. The term Brets or Britons refers to the native, traditionally Cumbric speaking people of southern Scotland and northern England as well as the Pictish speakers in Northern Scotland.
It seems that Cumbric could well have survived into the middle of the 12th century as a community language and even lasted into the 13th on the tongues of the last remaining speakers. Certain areas seem to be particularly dense in Cumbric place-names even down to very minor features. The two most striking of these are around Lanercost east of Carlisle and around Torquhan south of Edinburgh. If the 1262 names from Peebles do contain traces of Cumbric personal names then we can imagine Cumbric dying out between 1250 and 1300 at the very latest.