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).
Willa
Willa has been climbing in recent years. All-time it's been given to 32,848 U.S. babies, the 818th most common name by sound today, peaking at 889 in 2019, with 742 in 2025.
Willa has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).