Cassidy is a distinctive girls' name in England & Wales, ranking #586 in 2010 with 67 recorded births. The name reached its all-time peak in 2010 with 67 births ranking #586. Since 1996, the popularity has increased by 318.8%. In 2010, approximately 1 in every 4,792 girls born was named Cassidy. FALLING Recent data shows the name is currently falling.