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).
Cassius
Cassius climbed for decades and has been a steadily popular name ever since. All-time it's been given to 9,766 U.S. babies, the 1,027th most common name by sound today, peaking at 612 in 2021, with 504 in 2025.
Cassius has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).