Augustine is from the Latin augustus (majestic, venerable, exalted) — feminine form. Princess Augustine — modern Latin heritage naming. Augustine of Hippo's mother Saint Monica was a Christian saint herself.
Augustine 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 Augustine reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.