Where does “однополчанин” come from?
однополчанин (Russian) comes from Russian одно-, from Russian оди́н, from Old East Slavic оди́нъ, from Proto-Slavic edìnъ, from Proto-Balto-Slavic edīˀnas, from Proto-Balto-Slavic aiˀnas, from Proto-Indo-European óynos — one; single.
однополчанин (Russian): brother soldier
Ancestry of “однополчанин”, step by step