Tetrarch
‘a governor of a fourth part of a province’
Lexical development traced from the Tamil root:
E. tetrarke < O.E. tetrarche ‘ruler of one of four divisions of a kingdom or province’ < La.Lat. tetrarcha < tetrarches < Gk. tetrarkhēs ‘leader of four companies, ruler of four provinces’ < tetra ‘four’ + arkhein ‘to rule’ < aak < Tamil aracaṉ