Dictionary of Family Names

MASTEN, MOSTYN   (Welsh)   A place or house inclosed, from maes, a field, and din, inclosed, fortified.  Moestuin, in the Teutonic and Dutch, signifies a garden, a place cultivated.  The Gaelic dun, and the Welsh din, a fortified hill or fort, are synonymous.  The Saxon tun signifies an inclosure, a garden, a village, a town, and tun or tuin, in Dutch, a garden, a protected place.

Camden relates, that in the time of Henry VIII., an ancient worshipful gentleman of Wales being called at the panel of a jury by the name of Thomas-Ap-William-Ap-Thomas-Ap-Hoel-Ap-Euan Vaughn, etc., was advised by the judge to leave that old manner.  Whereupon, he afterward called himself Mostyn, according to the name of his principal house, and left that surname to his posterity.  Mostyn, a village in Flintshire, Wales.  On Mostyn hill, in Flintshire, Wales, is a remarkable monument to the sun, a place of Druid worship.