regicide
‘one who kills a king’
Lexical development traced from the Tamil root:
E. regecide < O.F. regal ‘royal’ < Lat. regalis ‘royal, kingly; of or belonging to a king, worthy of a king’ < rex ‘king’ + -cide < rehj < reg- < Tamil aracaṉ
regicide
English words derived from Tamil aracaṉ connoting 'rule'