Old Irish in the context of "Ogham"

Proto-Celtic, or Common Celtic, is the reconstructed ancestral proto-language of all known Celtic languages, and a descendant of Proto-Indo-European. It is not attested in writing but has been partly reconstructed through the comparative method. Proto-Celtic is generally thought to have been spoken between 1300 and 800 BC, after which it began to split into different languages. Proto-Celtic is often associated with the Urnfield culture and particularly with the Hallstatt culture. Celtic languages share common features with Italic languages that are not found in other branches of Indo-European, suggesting the possibility of an earlier Italo-Celtic linguistic unity.

Proto-Celtic is currently being reconstructed through the comparative method by relying on later Celtic languages. Though Continental Celtic presents much substantiation for Proto-Celtic phonology, and some for its morphology, recorded material is too scanty to allow a secure reconstruction of syntax, though some complete sentences are recorded in the Continental Gaulish and Celtiberian. So, the main sources for reconstruction come from Insular Celtic languages with the oldest literature found in Old Irish and Middle Welsh, dating back to authors flourishing in the 6th century AD.

Scottish Gaelic (/ˈɡælɪk/ GAL-ik; endonym: Gàidhlig [ˈkaːlɪkʲ] ), also known as Scots Gaelic or simply Gaelic, is a Celtic language native to the Gaels of Scotland. As a member of the Goidelic branch of Celtic, Scottish Gaelic, alongside both Irish and Manx, developed out of Old Irish. It became a distinct spoken language sometime in the 13th century in the Middle Irish period, although a common literary language was shared by the Gaels of both Ireland and Scotland until well into the 17th century. Most of modern Scotland was once Gaelic-speaking, as evidenced especially by Gaelic-language place names.

In the 2011 census of Scotland, 57,375 people (1.1% of the Scottish population, three years and older) reported being able to speak Gaelic, 1,275 fewer than in 2001. The highest percentages of Gaelic speakers were in the Outer Hebrides. Nevertheless, there is a language revival, and the number of speakers of the language under age 20 did not decrease between the 2001 and 2011 censuses. In the 2022 census of Scotland, it was found that 2.5% of the Scottish population had some skills in Gaelic, or 130,161 persons. Of these, 69,701 people reported speaking the language, with a further 46,404 people reporting that they understood the language, but did not speak, read, or write in it.

The Papar (Icelandic pronunciation: [ˈpʰaːpar̥]; from Latin papa, via Old Irish, meaning "father" or "pope") were Irish monks who took eremitic residence in parts of Iceland before that island's habitation by the Norsemen of Scandinavia. Their existence is attested by the early Icelandic sagas and recent archaeological findings.

Táin Bó Cúailnge (Modern Irish pronunciation: [ˈt̪ˠaːnʲ bˠoː ˈkuəlʲɲə]; "the driving-off of the cows of Cooley"), commonly known as The Táin or less commonly as The Cattle Raid of Cooley, is an epic from Irish mythology. It is often called "the Irish Iliad", although like most other early Irish literature, the Táin is written in prosimetrum, i.e. prose with periodic additions of verse composed by the characters. The Táin tells of a war against Ulster by Queen Medb of Connacht and her husband King Ailill, who intend to steal the stud bull Donn Cuailnge. Due to a curse upon the king and warriors of Ulster, the invaders are opposed only by the young demigod, Cú Chulainn.

The Táin is traditionally set in the 1st century in a pagan heroic age, and is the central text of a group of tales known as the Ulster Cycle. It survives in three written versions or "recensions" in manuscripts of the 12th century and later, the first a compilation largely written in Old Irish, the second a more consistent work in Middle Irish, and the third an Early Modern Irish version.

Eleanor Henrietta Hull also known as Eibhlín Ní Choill (15 January 1860 – 13 January 1935) was a writer, journalist and scholar of Old Irish.

Gofannon (Welsh pronunciation: [ɡɔˈvanɔn]) is a figure in Middle Welsh literature as a great metal worker and as the son of Dôn. His name can be compared with the Old Irish gobae (gen. gobann) ‘smith’, Middle Welsh / Cornish / Breton gof (pl. gofein) ‘smith’, Gaulish gobedbi ‘with the smiths’, all of which are cognate with Lithuanian gabija ‘sacred home fire’, gabus ‘gifted, clever’. His apparent counterpart in Irish mythology, Goibniu, in addition to his duties as a smith, also takes on the role of a divine hero who brewed an ale of immortality, in addition to being an architect and builder.

In Welsh mythology, Gofannon killed his nephew, Dylan Ail Don, not knowing who he was. One of the tasks given to Culhwch if he were to win the hand of Olwen was to get Gofannon to sharpen his brother Amaethon's plough.