Saint Diarmaid the Just (also known as Diermit, Dhiarmuit, Dermod, Diermedus, Diermetus, Diermitius, Diermitius) was a Catholic abbot of Inis Clothrann (Inchcleraun), Lough Ree, County Longford and of Faughalstown, County Westmeath and a famous Irish confessor of the late-sixth century.
He was of princely origin as he was seventh in descent from Nath Í, King of Ireland, who died in 428, and a member of the Hy-Fiachrach family from Connacht.
His mother was Dediva (also called Editua or Dedi or Deidi or Deighe or Deidiu or Deaga), daughter of Tren, son of Dubhthach moccu Lughair, who was a Chief Ollam of Ireland and royal poet of King Lóegaire mac Néill.
Wishing to found an oratory far from the day-to-day distractions of civilization, he selected the isolated island associated with the memory of Queen Medbh, Inchcleraun.
[3] The monastic school he founded kept up its reputation for fully six centuries after his death, and the island itself was famous for pilgrimages in pre-Reformation days.