Hanni is from the Vietnamese-Korean — possibly the iconic Vietnamese Hằng (moon) and the iconic Korean Han (Korea) + Ni (suffix). Princess Hanni — Vietnamese-Korean-Australian heritage naming.
Hanni 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 Hanni reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.