Eylül is the Turkish word for the month of September — borrowed from Hebrew Elul (the sixth month).
Used widely in modern Turkey.
Eylül 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.
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In Pythagorean numerology the letters of Eylül reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.