Tacitus wrote in Germania chapter 46: 'Peucini, quos quidam Bastarnas vocant, sermone, cultu, sede ac domiciliis ut Germani agunt.' ('The Peucini, who are sometimes called Bastarnae, are like Germans in their language, manner of life, and mode of settlement and habitation.')

Bastarnae was a Germanic people because they they spoke a Germanic language.