More about regina
The Latin noun rēgīna “queen” is obviously related to the Latin noun rēx (inflectional stem rēg-) “king,” but how rēgīna is derived from rēx is tricky. There is also a deceptive resemblance between rēx and rēgīna and Sanskrit rā́jan– “rajah, king” and rā́jñī– “queen, ranee” (rēgīna and rā́jñī– are not directly related). There is a definite connection, however, between Latin rēx (rēg-), rēgīna and the Celtic words for king, e.g., Old Irish rí (from rīks), and its stem ríg (from rīg–os). Rígain, the Old Irish word for queen, is cognate with rēgīna. Regina dates from Old English times.