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).
Simon
Simon has stayed fairly steady in American naming for generations. All-time it's been given to 70,444 U.S. babies, the 495th most common name by sound today, peaking at 1,653 in 2015, with 1,529 in 2025.
Simon has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).