Cassidy is a moderately popular girls' name in United States, ranking #280 in 2012 with 1,140 recorded births. The name reached its all-time peak in 1999 with 3,395 births ranking #99. Since 1996, the popularity has decreased by 59.9%. In 2012, approximately 1 in every 1,545 girls born was named Cassidy. STABLE Recent data shows the name is currently stable.