Olenna is from the iconic A Song of Ice and Fire novels — adapted by George R.R. Martin from the Hebrew Helena (light, torch). Princess Olenna — fantasy heritage naming.
Olenna 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 Olenna reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.