Amba (अम्बा) is the Sanskrit word for "mother." The eldest of three princesses of Kashi abducted by Bhishma for his half-brother Vichitravirya in the Mahabharata.
Amba 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 Amba reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.