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).
Hugo
Hugo has stayed fairly steady in American naming for generations. All-time it's been given to 37,518 U.S. babies, the 788th most common name by sound today, peaking at 837 in 2025, with 837 in 2025.
Hugo has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).