Rhian (Welsh) comes from Welsh rhiain, from Middle Welsh riein, from Proto-Brythonic rriɣėn, from Proto-Celtic rīganī, from Proto-Indo-European h₃rḗǵnih₂, from Proto-Indo-European h₃rḗǵs, from Proto-Indo-European h₃reǵ- — to straighten, to right oneself; right; just.