Cassidy is a distinctive girls' name in England & Wales, ranking #649 in 2004 with 46 recorded births. The name reached its all-time peak in 2010 with 67 births ranking #586. Since 1996, the popularity has increased by 187.5%. In 2004, approximately 1 in every 6,214 girls born was named Cassidy. FALLING Recent data shows the name is currently falling.