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).
Nadia
Nadia is now well below its former popularity. All-time it's been given to 46,618 U.S. babies, the 924th most common name by sound today, peaking at 1,923 in 2005, with 531 in 2025.
Nadia has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).