Cassidy is a moderately popular girls' name in United States, ranking #150 in 2003 with 2,235 recorded births. The name reached its all-time peak in 1999 with 3,395 births ranking #99. Since 1996, the popularity has decreased by 21.4%. In 2003, approximately 1 in every 817 girls born was named Cassidy. STABLE Recent data shows the name is currently stable.