Setna was a native of Munster, the son of Erc and Magna, a sister of St. David.

[1] He was a student of Senán mac Geirrcinn, and accompanied the saint to Inis Mor, where Senan established a monastery.

[2] A Breton folk story, an adaptation of a tale associated with Ciarán of Saigir, states that God asked Sithney to be the patron saint of girls seeking husbands, but Sithney said he would rather be the patron saint of mad dogs and get some rest.

[4] The sources Le Grand used borrowed heavily from the Life of Ciarán of Saigir; the sections regarding Sithney in Brittany are more reliable.

[1] William Worcester recorded in 1478 that the body of the saint lay within the church of Sithney.