Sai is from the Sanskrit sāī (साईं — saint, master) and modern Marathi feminine usage. Sai Tamhankar (born 1986) is a contemporary Marathi and Bollywood actress with over 20 leading roles across Marathi, Hindi, Telugu, and Tamil cinema since 2008. Over 1 million Instagram followers.
Sai 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 Sai reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.