Katayoun is from the Persian کتایون — possibly from Old Persian kata-yauna (Greek city-related, of the Greek). Katayoun is one of the queens of the Shahnameh (Ferdowsi, c. Persian feminine name.
Katayoun 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 Katayoun reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.