Marion is the medieval French diminutive of Marie — from the Hebrew Miryam ("beloved, star of the sea"). Marion Jones (born 1975) — American track sprinter whose 5 Sydney 2000 Olympic medals were stripped after admission of doping; subject of No Excuses memoir (2010). Marion Ross — Happy Days (1974). Maid Marion is the female lead of Robin Hood legend.
Marion 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 Marion reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.