How to read the band →
Solid line = floor (spellings that unambiguously belong to the group). Shaded band up to the dashed edge = ceiling (the most it could reach if every ambiguous spelling counted here).
Cassidy
Cassidy is now well below its former popularity. All-time it's been given to 86,298 U.S. babies, the 679th most common name by sound today, peaking at 4,406 in 1999, with 856 in 2025.
By sound, Cassidy also includes the spellings Kassidy.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).