The Proto-Indo-European word *h₃reĝ-
Word *h₃reĝ-
Meaning to extend, to stretch
See also Proto-Indo-European: *h₃rḗĝs ‘ruler, king’
Proto-Indo-European: *h₃reĝtos ‘right’
Synonyms *ten-, *reiĝ-

Comments
Mallory J.P. and Adams D. (2006)