Fergnae or Fergno Britt mac Faílbi was the fourth abbot of Iona (605–623). Fergnae was the first abbot of Iona to have come from outside Saint Columba's generation. Moreover, unlike his predecessors, he was not from the Cenél Conaill, the kin-group to which Columba belonged and he may also have been British and a bishop.C. Bourke, 'Fergna Epscop', Innes Review 51 (2000), pp. 68-71. Adomnán, in his Vita Columbae, says that he was 'a young man of good ability' and records that he witnessed one of Columba's miracles.Adomnán, Vita Columbae III.19. Fergnae died in 623, and was succeeded by Ségéne.
References
Bibliography Sharpe, Richard, Adomnán of Iona: Life of St. Columba (London, 1995)