A Christian; follower of Christ
Keirstyn is a modern creative spelling of Kirsten, which is the Scandinavian form of Christina. It ultimately derives from the Latin name Christianus, meaning a follower of Christ. This specific spelling variation gained some traction in the United States during the late 20th century as parents sought unique ways to render traditional names.
Less common today
Keirstyn isn't in the latest US Top 1000. It last peaked at #4,977 in 2001.
US births per 5-year period, 1990βpresent (SSA data).