Cassidy is a moderately popular girls' name in United States, ranking #199 in 2006 with 1,771 recorded births. The name reached its all-time peak in 1999 with 3,395 births ranking #99. Since 1996, the popularity has decreased by 37.7%. In 2006, approximately 1 in every 1,073 girls born was named Cassidy. STABLE Recent data shows the name is currently stable.