This chapter examines two small items of grammatical nature in the compilation now catalogued in the National Library of Ireland as MSS G2 and G3, which contains some of the earliest Irish-language material from the post-Norman period. Much of the compilation was written in the fourteenth century by the Fermanagh scribe Ádhamh Ó Cianáin, seemingly for his own use. The items in question reflect engagement with doctrine on cryptography and the letters of the alphabet as transmitted in some versions of the tract known as the De inventione linguarum (or litterarum), a text which circulated in several Continental Latin manuscripts from as early as the ninth century. The evidence that these entries provide for the relationship between the G2-G3 compilation and texts preserved in later Irish manuscripts will be discussed, as well as their significance for our understanding of Ádhamh's borader compilatory motives.