This study, led by Roberto Gonzalez de Viñaspre, Ibon Olaziregi, and Pedro Uribarrena, has compiled its findings in the book Toponimia histórica y contacto vasco-románico. Norte de Valdegovía y Ribera Alta (Álava), Berberana y Junta de Villalba de Losa (Burgos). The work has analyzed the oral tradition and historical documentation of the Burgos town of Berberana, clarifying the origin of the name of the Ebana river, indicating it predates Nervión.
“"The Nervión waterfall is a newly created name, appearing late in the 20th century."
The research demonstrates that, although most minor place names in the area between Álava and Burgos are Romance, the presence of Basque is notable. According to Gonzalez de Viñaspre, Basque appears in the earliest documents, albeit in the minority, indicating the existence of Basque-speaking communities.
Fieldwork and archival research have been fundamental. In ancient archives from the 10th and 11th centuries, such as the cartulary of Valpuesta, Basque toponyms like Urrundia have been found. This suggests that Basque was present in the area, although it was later lost and the toponyms transformed. The study also covered the historic municipality of Lakozmonte and nearby towns such as Subijana, Morillas, and Tetxa.
“"Romance had more demographic weight, but Basque is not an anecdote."
Furthermore, the research extended to Burgos, discovering a linguistic continuum from Osma to Berberana. 15th-century crusade bulls also confirm the presence of Basque, indicating the existence of monolingual Basque speakers in towns such as Osma, Fresneda, Morillas, Ormijana, or Axkoeta. The study has also found hybrid toponyms, such as Carragonesti, which combine elements of Castilian and Basque.
