Cassidy is a moderately popular girls' name in United States, ranking #168 in 2004 with 2,007 recorded births. The name reached its all-time peak in 1999 with 3,395 births ranking #99. Since 1996, the popularity has decreased by 29.4%. In 2004, approximately 1 in every 915 girls born was named Cassidy. STABLE Recent data shows the name is currently stable.