Zeuss, Johann Kaspar (1806–56), philologist, linguist, and founder of Celtic studies, was born 22 July 1806 in the village of Vogtendorf, near Kronach in Upper Franconia, Germany, fourth among six children of Michael Zeuss, stonemason, and Margaretha Zeuss (neé Hanna). Although he was brought up as a catholic, it seems that the parental marriage was a mixed one. He was instructed in Latin by the parish priest in his formative years, went to the village school in Höfles for five years, and then to the Latin school of Kronach for a further three. Between 1820 and 1825 he studied successively at the Progymnasium and then the Gymnasium at Bamberg. Graduating from the latter (1825) with the silver medal for distinction, he entered the University of Würzburg, where he matriculated in the faculty of theology in the spring of 1825. He stayed very briefly in the philosophy faculty of the Lyceum at Bamberg, but then entered the University of Munich, where he studied languages, philosophy, and theology. Among his eminent teachers were Döllinger and Schelling. He rapidly became a master of many languages, including Greek, Hebrew, Arabic, and Lithuanian.
In 1829 he obtained his first post as private tutor to the son of the Graf Montgelas. He passed his Lehramtprüfung in 1830 with distinction in philosophy and history. In 1832, he obtained the post of teacher of Hebrew at the Alt-Gymnasium (later the Wilhelms Gymnasium), Munich, where he continued his studies. His first book, Die Deutsche und die Nachbarstämme (‘The Germans and their neighbours’) was published in 1837, the printing of which he paid for himself. He was awarded a doctorate of philosophy from the University of Erlangen in August 1838, and in the following November applied for a teaching post at Erlangen or Würzburg. Finally, in 1839, he was appointed professor of history at the Lyceum in Speier, and in the same year he published Die Herkunft der Baiern von den Markomannen, in which he first evinced an interest in the Celts and their contribution to Germanic culture. He made several more applications to the Bavarian court in the following years for the post of librarian or archivist at Würzburg, Speier, and Bamberg, all of them rejected, probably because of some political statements which he had made in his second book. In 1847, he was appointed professor of history at the University of Munich and held a post at Bamberg.
His major opus, Grammatica Celtica, was published (1853) without prior notice to the world of scholarship. Zeuss had had it in preparation for thirteen years, making many journeys from Speier, where he lived, to the libraries of Karlsruhe, Darmstadt, St Gall, Milan, and other centres, where he transcribed, deciphered, and translated into Latin the thousands of vernacular glosses occurring in medieval manuscripts copied by Celtic monks on the Continent in the middle ages. The extreme difficulty of the Grammatica Celtica as a work of scholarship may perhaps have been responsible for the apparent indifference with which it was initially received, but it gradually revolutionised the study of the Celtic languages, and within a few years was greeted by John O'Donovan (qv) in his review of the work in the Ulster Journal of Archaeology in 1859 in the words: ‘The Irish nation has had no nobler gift bestowed upon them by any Continental author for centuries back than the work which he has written on their language.’ Bishop William Reeves (qv) said of it in the same publication: ‘Zeuss was the greatest benefactor that Irish literature can record in its list.’ The work is a masterpiece of comparative philology, which laid the foundations for the systematic study of the grammatical system of the Celtic languages, especially Old Irish. It was reedited by Ebel in 1871. After its publication in 1853 Zeuss devoted himself to preparing a second edition but was hampered by illness. An ascetic, he neither smoked nor drank alcohol, but usually filled his pockets with sweets and drank milk. He had a speech impediment which made it difficult for him to lecture. Ill health prevented him from accepting James Henthorn Todd's (qv) offer of a position at TCD.
Zeuss died 10 November 1856, aged 50, at Vogtendorf, where he was born. He was predeceased by almost all his family, who died of the same ‘spectre of the family’ which would take Zeuss himself – pulmonary tuberculosis. He never married, having devoted all his energies and his meagre income to the pursuit of scholarship. It seems that he was about to make a visit to Dublin at the time of his death. He is commemorated by a bronze statue in Kronach, where a school, the Kaspar-Zeuss gymnasium, and a street are named after him.