Career
He was notably the author of Irish Street Ballads published in 1939 and More Irish Street Ballads in 1965. He was part of a team which was sent to Kerry on Good Friday in a bid to seize radio equipment for communication with The Aud, a German ship transporting arms from Germany for the Easter Rising. Ó Lochlainn established the Candle Press in 1916.
He founded his own press, At the Sign of the Three Candles Press, in 1926.
He gave the aspiring piper Seamus Ennis his first job at this press, and Ennis collaborated with him on the Irish Street Ballads books He succeeded Seamus Ó Casaide as volunteer editor of Irish Book Lover in 1930.
He was an assistant in the Faculty of Modern Irish at University College Dublin from 1933–1943, where he later became professor of Irish Language and Literature. He was also associated with the founding of An Óige.
He died in a nursing home in Dublin and was buried in Glasnevin Cemetery.