Eithne (pronounced "en-yah") is from the Old Irish etne (kernel, grain). The mother of Lugh — the great Celtic god — and one of the most enduring Irish feminine names. Enya, the Irish singer (born 1961), is the Anglicized form.
Multiple saints and queens bore the name.
Eithne 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 Eithne reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.