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).
Willow
Willow has been climbing in recent years. All-time it's been given to 65,560 U.S. babies, the 137th most common name by sound today, peaking at 5,231 in 2021, with 4,786 in 2025.
Willow has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).