The 3000 or so Irish glosses are a vital witness to reconstructing old Irish, and also give us some insights into the Biblical interpretation of the early Irish church. An interesting gloss is written over 2 Corinthians 12:7, where Paul mentions his stimulus carnis, or thorn in the flesh. The Irish gloss reads, Cenngalar (headache). This may be an allusion to the Latin theologian Tertullian (d.220) who wrote that Paul’s thorn in the flesh may have been per dolorem, ut aiunt, auriculae uel capitis (a pain in the ear or head).
Like so many Irish manuscripts its survival was due to being taken to the continent by wandering Irish monks, while at home countless manuscripts and libraries were destroyed by the Vikings. Manuscripts like the Codex Paulinus were valuable study tools and welcome reading to the many Irish scholars in Germany and elsewhere. As the writing style in Europe evolved the insular miniscule hand used in this manuscript became archaic and hard to read, so these manuscripts sat unused in European monasteries and libraries. Dusty relics like these speak of the vibrancy of the early Irish church and her many pilgrims for Christ.
For further details see:
Ó Néill, Pádraig P., “The Old-Irish glosses of the prima manus in Würzburg, m.p.th.f.12: text and context reconsidered”, in: Richter, Michael, and Jean-Michel Picard (eds.), Ogma: essays in Celtic studies in honour of Próinséas Ní Chatháin, Dublin: Four Courts, 2002. 230–242.
Breen, Aidan, “The Biblical text and sources of the Würzburg Pauline glosses (Romans 1–6)”, in: Ní Chatháin, Próinséas, and Michael Richter (eds.), Irland und Europa im früheren Mittelalter: Bildung und Literatur / Ireland and Europe in the early Middle Ages: learning and literature, Stuttgart: Klett-Cotta, 1996. 9–16.
Ní Chatháin, Próinséas, “Notes on the Würzburg glosses”, in: Ní Chatháin, Próinséas, and Michael Richter (eds.), Irland und die Christenheit: Bibelstudien und Mission. Ireland and Christendom: the Bible and the missions, Veröffentlichungen des Europa Zentrums Tübingen. Kulturwissenschaftliche Reihe, Stuttgart: Klett-Cotta, 1987. 190–199.