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).
Danny was more common in the past and has since settled at a lower, steady level. All-time it's been given to 313,977 U.S. babies, the 680th most common name by sound today, peaking at 9,396 in 1954, with 942 in 2025.
By sound, Danny also includes the spellings Dannie, Dani, Danni.