Diah is the Javanese-Indonesian honorific for "lady" or "esteemed woman." Used as a feminine name and as a prefix-title.
Diah Permatasari is the Indonesian actress.
Diah 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 Diah reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.