This piece of work is intended as a contribution to the linguistic study of personal names throughout the Late Middle Ages in Galicia (Northwest of the Iberian Peninsula). After exploring several types of sources, non-literary edited documents ranging over a chronological period between the 8th and the 12th centuries were chosen. The compilation of data was carried out after reviewing the original documents in order to correct editing mistakes. The final result consisted of nearly 10000 onomastic sequences, including about 18000 subsequent occurrences. Then, research into the system of personal names and its evolution was initiated. Among the topics explored were the change from the use of a single name to the use of a second name, the creation of this second name by morphological procedures (patronymic suffix -iz, i.e. modern -ez) or through the use of bynames (nicknames, petnames and professional names), place names and ethnic names. This project also offers an etymological study of the data and a dictionary of proper names with more than 2000 entries.