Charles Dillon, editor of the Foclóir Stairiúil Gaeilge [Historical Dictionary of Irish], writes (for the Royal Irish Academy’s library blog) about Johann Kaspar Zeuss (1806-1856), whose magnum opus Grammatica Celtica (1853) “established incontrovertibly through the study of Old Irish sources the relationship of the Celtic languages to the Indo-European family”:
This was the age of ‘Celtomania’, a phenomenon which for want of learned, scientific and empirical research into their origins, had ascribed various fanciful and unproven ancestry to the Celtic languages, often relating them to mysterious peoples and exotic tongues. Only tentatively, by the time of Zeuss, had serious scholars suggested that Celtic was related to the Indo-European family, and it is notable that the great philologists Jacob Ludwig Grimm (he, with his brother Wilhelm, of fairytale fame) and Franz Bopp did not include Celtic in their great comparative surveys of German, Sanskrit, Zend (Avestan), Greek, Latin, Lithuanian and Gothic, which traced the ancestry of the premier European languages eastwards to the heart of India. […]
It was to this gap in the knowledge of the situation of Celtic that Zeuss addressed himself, setting about his task through his study of Old Irish sources. What is perhaps most remarkable by today’s standards is that he never visited Ireland, and it is questionable whether indeed he ever met an Irish speaker. His approach to the problem led him ad fontes; he travelled to libraries across Europe wherein were housed the earliest examples of written Irish. These were in the form of glosses, such as those found in Würzburg, Karlsruhe, Milan and Turin (mostly from the 8th century, but some in the so-called prima manus, from the 7th), in which commentaries in Irish on, for example, the epistles of Paul are found between lines and in text margins. Zeuss transcribed and interpreted these and other such examples and from his analysis he was able to lay out in Grammatica Celtica, for the first time, the grammar of the language. In his return to the earliest extant forms of the language, Zeuss was a pioneer; earlier in the eighteenth century the glosses had been identified as Irish but mistakes had been made in their interpretation. Zeuss brought to their study his modern training that enabled him to tackle the scientific study of any language. His reliance on the glosses is almost absolute, and he barely refers to any extant scholarship in Celtic, obviously preferring to build all his conclusions solely on the foundation of the sources.
Studying Old Irish made me happier than almost anything else I did in grad school, and the very words “Würzburg glosses” send me back forty years and more to the period when I was carrying around my beat-up copy of Thurneysen’s Grammar of Old Irish (1970 reprint of the 1946 translation); I now learn that Thurneysen’s work would have been impossible without his predecessor Zeuss, and I join Dillon in honoring him. Thanks, Trevor!