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).
Antonio was more common in the past and has since settled at a lower, steady level. All-time it's been given to 264,970 U.S. babies, the 384th most common name by sound today, peaking at 5,089 in 1997, with 2,058 in 2025.
Antonio has no common alternate spellings by sound.