The main focus of this chapter is on the early literate tradition in the Irish language and how this tradition was born in the multilingual interaction with a neighbouring written culture, namely that of Latin in the island of Britain. Since a crucial part of this interaction with Ireland happened through British inter mediar ies or took place in Britain, both regions of the western archipelago will be considered in this survey, though the very different historical and sociolinguistic scenarios in the two islands necessitates looking at each separately. In addition to Latin in the specific flavour as spoken in ancient Britain, here after referred to as British Latin, the two main languages are Irish and British. Irish (also called Goidelic) and British (also called British Celtic or Brythonic) are two distinct branches of the Celtic branch of the Indo- European languages, the others being Celtiberian and Gaulish (including Lepontic), which died out before the middle of the first millennium ce.1 However, Irish and Latin cannot be looked at in isolation and aspects of the oldest written stages of other languages will also have to be considered briefly.