Agatha (Ἀγάθη) is from the Greek agathos, meaning "good" or "kind." Saint Agatha of Sicily (c.
Agatha Christie (1890-1976), the British mystery writer, is the most internationally known bearer — the best-selling novelist of all time.
Agatha 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 Agatha reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.