Bertha is a female Germanic name, from Old High German berhta meaning "bright one". It was usually a short form of Anglo Saxon names Beorhtgifu meaning "bright gift" or Beorhtwynn meaning "bright joy". . The name occurs as a theonym, surviving as Berchta, a figure in Alpine folklore connected to the Wild Hunt, probably an epithet of *Frijjō in origin. Bertha appears as a Frankish given name from as early as the 6th century. https://en.wikipedia.org/wiki/Bertha