Halla is from the Old Norse hǫll (hall, stone) — feminine form of Hallr. Halla Eyjólfsdóttir (c. 935-?) was the medieval Icelandic woman known from the Landnámabók. Halla Tómasdóttir (born 1968) is the current President of Iceland (elected 2024).
Used widely in modern Iceland.
Halla 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 Halla reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.