Cassidy is a moderately popular girls' name in United States, ranking #250 in 2013 with 1,274 recorded births. The name reached its all-time peak in 1999 with 3,395 births ranking #99. Since 1996, the popularity has decreased by 55.2%. In 2013, approximately 1 in every 1,377 girls born was named Cassidy. STABLE Recent data shows the name is currently stable.