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).
Jonas
Jonas has stayed fairly steady in American naming for generations. All-time it's been given to 28,588 U.S. babies, the 1,021st most common name by sound today, peaking at 1,256 in 2008, with 476 in 2025.
Jonas has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).