Masako (政子) combines the Japanese masa (correct, government) and ko (child). Hojo Masako (1156-1225) was the wife of Minamoto no Yoritomo, the first Shogun of Japan. After her husband's death, she took Buddhist vows but continued to wield supreme political power as ama-shogun ("the Nun Shogun") through her father, brother, and sons. Effectively the first female ruler of Japan in the warrior era.
Featured throughout Azuma Kagami and Japanese historical drama.
Masako 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 Masako reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.