The poem consists of three-line englyn stanzas and exists in several versions all in Middle Welsh.
The earliest surviving version is in the Black Book of Carmarthen, completed around 1250, though the poem may have been composed in the 10th or 11th century.
The poem's subject, Geraint mab Erbin, was a popular figure in Welsh tradition and is known through a variety of subsequent sources.
[2][4] Geraint son of Erbin makes heavy use of repetition in celebrating Geraint's deeds at Llongborth, which may be identified with Langport, Somerset, or Portsmouth, Hampshire though llongborth may refer to a "ship harbour", akin to the Old Norse longphort in Ireland.
[6] This is the first known reference to Arthur as emperor, a title used frequently in later works but absent in the early material.