Cassidy is a distinctive girls' name in England & Wales, ranking #696 in 2001 with 36 recorded births. The name reached its all-time peak in 2010 with 67 births ranking #586. Since 1996, the popularity has increased by 125.0%. In 2001, approximately 1 in every 7,444 girls born was named Cassidy. FALLING Recent data shows the name is currently falling.