Usual English form of Dorothea. The name was not used in the Middle Ages, but was taken up in the 15th century and became common thereafter. It was borne by the American film star Dorothy Lamour (1914–1996, born Dorothy Kaumeyer).
English and Scottish: 1. nickname for a cheerful person, from Old English blīðe ‘merry’, ‘cheerful’. 2. habitational name from any of several places called Blyth or Blythe, especially Blyth in Northumberland, named for the rivers on which they stand. The river name is from Old English blīðe ‘gentle’, ‘pleasant’.