Marilyn is a 19th-century English blend of Mary + Lyn — combining the Hebrew Mary ("beloved") with the English suffix. Marilyn Monroe (1926-1962) — born Norma Jeane Mortenson — the American actress and cultural icon whose 29 films grossed over $200 million in her lifetime; her image remains one of the most reproduced in the world. Marilyn Manson is male; the name has been overwhelmingly feminine since the 1920s.
Marilyn 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 Marilyn reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.