T. F. O'Rahilly

[4] De Valera commented on this unusual sight:If O'Rahilly had been reading Greek I would not have been too surprised; I could attempt that myself.

He spent a year teaching Irish at University College Dublin, before taking up a permanent position as a clerk in the Four Courts in 1906, where he stayed until 1919.

Fellow Celtic languages scholar and lecturer of Trinity College, Dublin Eleanor Knott described his work during this period:His unsurpassed knowledge of modern Irish dialects and manuscript literature was acquired in his early manhood when as a civil servant his chosen studies had perforce to be relegated to evenings, weekends and vacations.

Unceasing application during this period together with recurrent attacks of influenza brought about a definite decline in his health and this should be taken into account in considering a characteristic asperity in criticising the work of other scholars.

[7]In 1919 he entered academic life in a full-time capacity upon taking up his first professorship in Irish at Trinity College, Dublin (1919–1929).

He was appointed research professor in Celtic languages in 1929 at University College Cork and stayed in this position until 1935.

His wife believed that his death was due to overwork and burned many of his remaining papers at their home.

His collection of books, correspondence, and Irish manuscripts, including an annotated draft of the 1937 Constitution of Ireland, were bequeathed to the Queen's University of Belfast.

He argued that the first three groups spoke Brittonic languages, and that many of Ireland's 'pre-Gaelic' peoples flourished for centuries after 100 BC.

[10] Although highly influential, O'Rahilly's theory has been challenged by historians, archaeologists and linguists—such as Kenneth H. Jackson[11] and John T. Koch[12]—and it is no longer accepted.

[17]This view has more recently been challenged by Nicholas Williams, who suggests that Manx is Gaelic pidginized by early contact with Norse, long before there was any English spoken on the Isle of Man.