How Christians first came to be in Ireland is not clear. The most likely way is that Christian soldiers, sailors, merchants, travellers, some perhaps refugees or even slaves, came on the sea-routes from Gaul and further afield.
On the other hand Old Irish words like Easter, priest and vespers, were taken over from Britain and this, coupled with known connections between Ireland and Wales, suggests another route to Ireland.
Monks and hermits could have set up in Ireland even as early as the mid-fifth century. The first monasteries appeared in Britain at this time on the fringes of the Roman occupation, in Wales, southern Scotland and Cornwall.
If the monasteries in Britain and Ireland owe something to Gaul, they in turn owe everything to Egypt,(and perhaps a little to Syria). The connections are elusive, consisting of textual forms and variant Gospel readings. But the pervasive strong asceticism (especially of the ‘deserts’), the building of cells, and popularity of the ‘St Anthony met St Paul theme’ on carved crosses is extremely suggestive and in the end overwhelming. Within a century it had taken over Ireland and the Irish church with it.
However the language used in Ireland was Latin. The training of Irish monks in Wales may have helped here. Important early Irish words reveal Latin origins: words for church are ‘kill’ or ‘cell’ from Latin cella, ‘teampall’ from templum, ‘disert’ for hermitage from deserta. Whatever the connections Irish had with the church at large in the East, we must remember that the Irish church was always, from the beginning, rooted in Latin Christianity.
Many early founders began as hermits. Others came in due course to share his life. The hermit’s dwelling (cell) may have been made only of brush or wattle. A monastery would often develop from such humble beginnings.
Such was the natural geography of the land, communication and travel, water was the obvious means of transport. Ireland was not so much, so to speak, solid land but a sea and river system with earth in between. Access to water was a primary consideration.
Viking raids on Ireland began about 800 disrupting social and religious life. The next 200 years saw both internal and external warfare; the number of saints as well as monasteries dropped dramatically.