Cassidy is a moderately popular girls' name in United States, ranking #247 in 2014 with 1,311 recorded births. The name reached its all-time peak in 1999 with 3,395 births ranking #99. Since 1996, the popularity has decreased by 53.9%. In 2014, approximately 1 in every 1,362 girls born was named Cassidy. STABLE Recent data shows the name is currently stable.