Cassidy is a distinctive girls' name in England & Wales, ranking #623 in 2007 with 56 recorded births. The name reached its all-time peak in 2010 with 67 births ranking #586. Since 1996, the popularity has increased by 250.0%. In 2007, approximately 1 in every 5,466 girls born was named Cassidy. FALLING Recent data shows the name is currently falling.