Old Breton guiler, guilerou, guileri and Old Welsh gueleri

This article argues that OBr guiler, guilerou, guileri, OW gueleri ‘calendar’ are not loans directly from Lat. uig(i)liarium ‘festive calendar’, but are borrowed from OIr. félire instead. The manuscripts in which these words appear have to be studied in the wider context of the medieval Celtic glossing tradition.