Dorothea is from the Greek dōron (gift) + theos (god) — same elements as Theodora in reverse order. Dorothea Lange (1895-1965) — *American documentary photographer whose Dust Bowl-era images — most famously Migrant Mother (1936) of Florence Owens Thompson — defined the visual memory of the Great Depression. Worked for the Farm Security Administration alongside Walker Evans and Marion Post Wolcott. Dorothea Brooke is the heroine of George Eliot's Middlemarch (1871-72) — widely considered the greatest English novel. Dorothea Dix (1802-1887)* — American activist whose 1841 testimony to the Massachusetts legislature founded the modern asylum reform movement.
Subject of Linda Gordon's Dorothea Lange: A Life Beyond Limits (2009).
Dorothea does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Dorothea reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.