Astou is from the Wolof / Pulaar Astou — West African rendition of Arabic Aisha / 'Aaʾisha (عَائِشَة — living, alive). Astou is one of the Senegalese feminine names — central to traditional West African Muslim heritage.
Astou 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 Astou reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.