Lia is the Italian and Portuguese short form of Leah (Hebrew, "weary") or of names ending in -lia like Amelia, Cecilia, or Natalia.
Lia entered the U.S. top 1000 in 1969 and has been climbing steadily. Today it sits in the U.S. top 250.
Lia 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 Lia reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.