Kirstie is the Scottish diminutive of Kirsten / Christine — from the Greek christianos ("follower of Christ"). Kirstie (2013) — TV Land sitcom. Kirstie is the warmer Scottish-vernacular form of the more formal Kirsten and Christine; it surged in the UK and US during the late 1980s and is now a vintage-of-the-80s revival candidate.
Kirstie 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 Kirstie reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.