Monserrat is from the Catalan Montserrat — from Latin mons serratus — compound of Latin mons (mountain) + serratus (serrated/sawn). Monserrat is one of the Catalan feminine names — central to traditional Catalan Catholic + Hispanic heritage.
Monserrat 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 Monserrat reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.