Marnie is a Scottish-English diminutive of Marina or Margaret — also linked to the Hebrew Miryam ("beloved, bitter, star of the sea"). Marnie Cotton — Hollyoaks character. "When Marnie Was There" (2014) — Studio Ghibli animated film directed by Hiromasa Yonebayashi based on the 1967 Joan G.
Marnie 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 Marnie reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.