Ua Casaide (Caiside), Gilla-Mo-Dutu (d. p. 1150), poet and dynastic historian, came from Ard Breccáin (Ardbraccan, Co. Meath), but his genealogy is unknown. He was based on Daminis (Devenish), an island on Lower Lough Erne (Co. Fermanagh), where he composed his longest work, the metrical ‘Banshenchas’ (lore of women), a catalogue of the famous women of Ireland and the dynasties into which they married covering the period from early historic times up to 1147. Eleven other poems are also attributed to him. Among them may be mentioned a poem on the high-kings of the Christian era, ‘Éri óg-inis na náem’, composed in 1143, as well as two others on the same subject, ‘Cuibdius Comanmann na Ríg’ (unpublished) and ‘Sé rígh déc Éogain anall’. According to a note inserted by a scribe into a copy of the first-mentioned poem, the poet was ‘blind and flat-faced and he never chanted falsehood or a crooked history’. He also composed three poems to his patron, St Laisrén (Mo-Laisse) (qv) of Devenish, which are preserved in one manuscript of the saint's Irish Life (BL, Add. MS 18205). Gilla-mo-Dutu's death is not recorded in any of the annals.
O'Brien, Corpus geneal. Hib., 156; Plummer, Bethada náem nÉrenn, i, 190–290; M. C. Dobbs, ‘Ban-Shenchus’, Rev. Celt., xlvii (1930), 282–339; xlviii (1931), 163–234; xlix (1932), 437–89; R. A. S. Macalister (ed.), Lebor Gabála Érenn (5 vols, 1938–56), 413, 562–65; M. Ní Bhrolcháin, ‘The prose Banshenchas’ (Ph.D. thesis, NUI (UCD), 1980), 5–9, 24; A. Connon, ‘The Banshenchas and the Ui Néill queens of Tara’, Smyth (ed.), Seanchas (2000), 98–108