Mirabai is from the Sanskrit mīrā (sea, ocean, or "wonderful" in Rajasthani) + bāī (Hindi honorific for a respected woman). Mirabai (c. "Mere to Giridhar Gopal" (My only beloved is Krishna) is among the most-recorded Indian devotional songs of the 20th century.
Mirabai 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 Mirabai reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.