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).
Heidi
Heidi is now well below its former popularity. All-time it's been given to 155,772 U.S. babies, the 668th most common name by sound today, peaking at 4,749 in 1972, with 995 in 2025.
By sound, Heidi also includes the spellings Heidy.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).