Eun (은) is a Korean syllable written with several possible hanja.
Eun is among the most common syllables in Korean girls' names. The K-pop singer IU's real name is Lee Ji-eun. As a single-name in Western use, Eun is rising as Korean families bring the syllable forward as a standalone.
Eun 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 Eun reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.