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).
Sebastian
Sebastian climbed for decades and has been a steadily popular name ever since. All-time it's been given to 218,463 U.S. babies, the 33rd most common name by sound today, peaking at 10,325 in 2016, with 8,615 in 2025.
Sebastian has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).