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).
Heather
Heather is now well below its former popularity. All-time it's been given to 527,387 U.S. babies, the 1,820th most common name by sound today, peaking at 24,366 in 1975, with 177 in 2025.
Heather has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).