This dissertation focuses on the Old High German (OHG) 1st person plural ending -mes, its origin, history and philological evidence. This ending is traditionally described as having an e-vowel (long e-vowel), which is hard to account for when comparing it to attested verb endings in the other Germanic languages as well as the reconstructed verb system of Proto-Indo-European. This ending does not survive into later stages of German. Vowel length in Old High German is difficult to assess from philological evidence as OHG manuscript scribes typically do not indicate vowel length in unstressed syllables. It turns out that the crucial evidence for the phonological shape of the ending is the orthography of one particular 9th century manuscript, Cod. Sang. 916, which contains the interlinear glosses to the Rule of the Benedictine monks. In this text etymological long vowels are denoted with double writing, i.e. e is denoted ee, but not consistently. The dissertation is thus structured: First I account for the origin of the Germanic verb endings in Proto-Germanic and Proto-Indo-European. I focus especially on the 1st person plural category and the variation of endings observed in different IndoEuropean languages. I then discuss the 1st person plural ending in Germanic and OHG in particular and account for some variations found in certain texts. I critically review previous theories about the origin of the ending. I take a close look at the manuscript Cod. Sang. 916. and analyze all the cases of long vowels occurring in this manuscript and compare their distributional patterns in the context of philological facts such as division into quires and contributions of various copyists and scribes. I challenge the previous assumption about the phonological shape of the ending and argue that the evidence for the length of the vowel in the ending is ambiguous. I conclude that for some of the earlier scribes or copyists responsible for the text in this manuscript the vowel in the ending was short. Finally I reevaluate the previous ideas about the origin of the ending in light of the results and propose my own alternative hypothesis based on my findings. 1