An Etymological Dictionary of the German Language/Annotated/Reihe
Reihe, feminine, from the equivalent Middle High German rîke, feminine, ‘row, line,’ allied to Middle High German rîhen, Old High German rîhan, ‘to range, put on a thread, fix,’ to which Middle High German rige, feminine, ‘row, line,’ Old High German rī̆ga, ‘line, circular line,’ and Dutch rij, ‘row,’ are akin. Anglo-Saxon râw, ‘row, line’ (Gothic *raiwa, for *raigwa, allied to *reihwan), whence English row is also probably connected with these. The Teutonic root rī̆hw, raihw, is related to Sanscrit rêkkâ, ‘streak, line’ (Aryan root rikh).