The title figure of Waltharius, an exclusive research subject of German Studies since the time of the Brothers Grimm, has become interesting for other philologies as well over the last 120 years, repeatedly in the form of "border crossings”. However, it has been impossible to reach a consensus even in the most elementary questions. Romance Studies is directly involved due to the problem complexes of Gualter del Hum, Gaiferos and the mother tongue of the Waltharius poet. Additional border crossings, however, are required to conduct new research on these problem complexes. This has become evident on the basis of new linguistic and onomastic observations in this book. Thus, almost an all-round monograph on one of the most multifaceted figures of medieval literature has evolved.