As Ireland's contribution to the international enterprise of compiling a "new Du Cange", the Royal Irish Academy has for nearly a generation been sponsoring the Dictionary of Medieval Latin from Celtic Sources project. This venture is designed to provide, for the Celtic territories, the lexicographical coverage of Medieval Latin that is (for example) coming to be furnished for German-speaking lands by the Mittellateinisches Wörterbuch, or for England by the British Academy's well-known DMLBS venture.

NCLCL, the Non-Classical Lexicon of Celtic Latinity (1st volume: letters A to H), by Anthony Harvey and Jane Power, offers a detailed, authoritative description, in standard lexicographical form, of the etymology, meaning and usage of thousands of words found in the DMLCS electronic archive that are absent altogether from the Oxford Latin Dictionary, having been coined after the period covered by that work. NCLCL also embodies a comprehensive register of words that are found in standard Latin but that appear, in texts of Celtic provenance, in orthographies or forms that cannot be accounted for by mainstream European developments in Medieval Latin.