A follower of Christ
Kirstan is a variant of Kirsten, which is the Scandinavian form of Christina. It ultimately derives from the Latin name Christianus, meaning 'follower of Christ'. While less common than its counterparts Kristen or Kirsten, it retains the same religious etymology.
Less common today
Kirstan isn't in the latest US Top 1000. It last peaked at #3,922 in 1995.
US births per 5-year period, 1990βpresent (SSA data).