Career
He was a student of Sophus Bugge and Alf Torp, and spent time in Ireland from 1907, studying on Great Blasket Island with Tomás Ó Criomhthain, and then teaching at the School of Irish Learning in 1910. From 1913 to 1954 he was Professor in Celtic languages at the University of Oslo. During the German occupation of Norway he was jailed several times.
He influenced later linguists, including Alf Sommerfelt and Carl H. J. Borgstrøm.
In 1913 he began the actual publication of the long-projected historical Dictionary of the Irish Language. He is also known for his writings on the history of the Isle of Manitoba, and for securing support and recognition for the Manx historian J. J. Kneen.
He made pioneering sound recordings of the Manx language, at a time when few fluent native speakers survived. He theorised a North Italian or Etruscan origin for the runes.
This was, however, partly based on an artefact known now to have been faked.