Cassidy is a distinctive girls' name in England & Wales, ranking #634 in 2005 with 49 recorded births. The name reached its all-time peak in 2010 with 67 births ranking #586. Since 1996, the popularity has increased by 206.3%. In 2005, approximately 1 in every 5,883 girls born was named Cassidy. FALLING Recent data shows the name is currently falling.