Morena is from the Italian and Spanish moreno (dark-haired, brunette) — also the Portuguese/Brazilian morena (dark-haired beauty). Morena Boriana — modern Italian figure. La Morena — iconic flamenco song.
Morena 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 Morena reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.