Pure lake
Kaselyn is a modern American invented name. It likely combines the prefix 'Kase' (often derived from the Greek name Katherine, meaning 'pure') with the popular 'lyn' suffix (derived from the Welsh word for 'lake').
Less common today
Kaselyn isn't in the latest US Top 1000. It last peaked at #10,098 in 2015.
US births per 5-year period, 1990βpresent (SSA data).