Dorthea is a name of Germanic origin, derived from the Old German words 'thodor' meaning "people" and 'helm' signifying "helmet". This name was borne by several early saints and martyrs in Christian history, which contributed to its popularity during the Middle Ages in Europe. The most notable being Saint Dorothy, who is said to have been martyred in the 4th century under the Roman Emperor Diocletian. Over time, Dorthea has evolved as a distinct name from its root form Dorothea, and both names have been popular choices for girls across various cultures.
"Dorthea's popularity as a baby name peaked between 1913 to 1924, with over 20 births per year for several years during that period. However, it has since declined significantly, with only 5 births each year from 2002 onwards."