Context
Eilean Trostain denotes a small island off the western coast of North Uist. No archaeological remains that might have contributed to our understanding of the early Christian presence on the island have been found. However, it may be significant that a possible burial cairn of an unknown date is located directly adjacent to the island on the mainland ([simple_tooltip content='Armit, I. 1996. 'Camas a' Chaisteil (North Uist parish) cairn, hut-circle', Discovery Excav Scot, 1996, 106.']Armit 1996, 106[/simple_tooltip]).

Discussion
The lack of early references and archaeological evidence makes it difficult to ascertain the history of this site with any certainty and it is possible that the second element in fact represents a common noun; [simple_tooltip content='Scottish Gaelic']G[/simple_tooltip] trostan ‘a pillar’. However, the potential commemoration in the name of a saint, Trostan, perhaps to be equated with St Drostan (Troscán, Trostan and Drostan may ultimately be the same names; see Trostan), is peculiar enough in its own right to warrant further consideration. [simple_tooltip content='DoSH Butter, R., Clancy, T.O. & Márkus, G. 2010-3. ‘Commemorations of Saints in Scottish Place-Names’ <https://www.saintsplaces.gla.ac.uk/>.']DoSH[/simple_tooltip] categorises this place-name as ‘maybe’ containing a dedication to the saint; if the identification is accurate, the name would represent the only dedication to St Drostan in the Hebrides since his cult is predominantly based in eastern Scotland (also see [simple_tooltip content='Plumb, P. 2016. ‘“Over the storm-swelled sea”: Early Medieval Ecclesiastical Migration from Northern Britain to Ireland’ (PhD Thesis, University of Edinburgh).']Plumb 2016, 183-98[/simple_tooltip] for further discussion of the commemoration of St Drostan).

It may be significant that in the Book of Leinster genealogies of saints St Troscán is listed as one of ‘the seven sons of one Oéngus, who are said to have come to Ireland from Scotland and to have founded churches in the Meath-Leinster area’ ([simple_tooltip content='Ó Cróinin, D. 1981. ‘The Oldest Irish Names for the Days of the Week?’ Ériu, vol. 32, 95-114; Clancy, T.O. 2008. ‘Deer and the early church in North-Eastern Scotland’, in Forsyth, K. (ed.) Studies in the Book of Deer (Dublin).']Ó Cróinín 1981, 104; also see Clancy 2008, 363-97[/simple_tooltip]). One of the other sons listed is St Torannán, the saint commemorated in Tarransay NB025913, off the coast of Harris. The same saint has also been associated with Teampull Chaluim Chille. Is an association between the commemoration of these two saints possible? See Paible for further discussion of sites on the western coast of North Uist.

Other resources
Saints in Scottish Place-Names Troscán mac Óengusa
Canmore ID 108252