Late medieval Christianity in Gaelic Ireland was characterised by a revival in the political and religious fear from the 1450s onwards really. In the political sphere, Gaelic Ireland had a revival because England was preoccupied with wars with France, and internally with the War of the Roses later on - this led to a weakening of the Pale (the English stronghold in Ireland) and a resurgence in Gaelic Ireland. This was matched by a spiritual resurgence which we see very much in what was known as ‘the observant reform’ which was a reform of the mendicant orders like the Franciscans and the Dominicans. Many, many friaries were set up all around the country and Gaelic Ireland on the whole experienced a resurgence in this regard.
One particularly useful way of examining the religious ideas of the Gaelic Irish is in the poetry of the bardic poets - a professional band of poets. These poets were, in the main, laymen, and were not priests or brothers. And even though they composed praise poetry for their secular patrons, they dedicated one tenth of their art to God, so we are fortunate enough to have a large corpus of Gaelic religious poetry. The themes that are treated-of by the Gaelic bardic poets reflect broader European devotional trends, rather than what we sometimes understand as Celtic spirituality per se today which is very interesting. And, in this regard it is important to note that when they treat of saints and devotion to the saints that the saints that they actually mention are not so much saints like Patrick, Brigid and Columcille and Ciaron and so on, but actually European saints that were popular with the mendicant orders, like Francis, Dominic, also the 12 Apostles and female saints like Saint Margaret and Saint Catherine of Alexandria. Mainstream European devotions had an effect on the Gaelic poetry of the bardic poets, especially devotions like the Cult of the Five Wounds which spread across Europe in the 14th and 15th centuries, and this had a huge impact on the poetry of the bardic poets. Sometimes what they do though is they take a broad theme and they actually gaelicise it which actually leads to an enrichment of the understanding of the particular theme in question.