Doreen is a variant of Dora, ultimately derived from Dorothy. Dorothy originates in Greek language and means "God's gift". It was derived from nowadays much less popular name Dorothea. In the United States the name Dorothy was the most popular in the first half of the 20th century, thanks to L. Frank Baum's novel The Wonderful Wizard of Oz, published in 1900 and introducing the character of Dorothy Gale. Later on, in 1939, the novel was made into a film simply called The Wizard of Oz.