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).
Koa
Koa has been climbing in recent years. All-time it's been given to 8,548 U.S. babies, the 558th most common name by sound today, peaking at 1,413 in 2025, with 1,413 in 2025.
Koa has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).