Where does “sipahi” come from?
sipahi (Turkish) comes from Ottoman Turkish سپاهی, from Persian سپاهی, from Persian سپاه, from Proto-Iranian *cwáHdah, from Proto-Indo-Iranian *ćwáHdʰaH, from Proto-Indo-European ḱwéh₁-dʰ-o-h₁.
Ancestry of “sipahi”, step by step