The Sarmatians or Sauromachae were the ancestors
of the Sclavonian tribes,…, the Poles, Russians, Bohemians, etc., who continue to this day a
distinct and separate people, extremely different in their character, manners, laws and language, from the other race, which was that of the Celts, from whom… were uniformly descended the old inhabitants of Gaul, Germany, Scandinavia, Britain and Spain, who were all
included by the ancients under the general name of Hyperboreans/ Scythians/Celts(Basques), being all originally of one race and nations, and having all the same common language, religion, laws, customs and manners”.31 German scholar Johannes Wachter (1663–1757) distinguished three distinct groups of Scythians among the peoples of Europe – the northern
Scythians proper, the western Celtae and the Germanic Celto-Scythians – and characterized the Celtic tongue as “the final stage of a united Germanic language before the evolution of its various dialects”
https://dspace5.zcu.cz/bitstream/11025/6401/1/Budil.pdf