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).
Rhett has climbed over the years and is holding near its high. All-time it's been given to 36,920 U.S. babies, the 360th most common name by sound today, peaking at 2,554 in 2021, with 1,955 in 2025.
Rhett has no common alternate spellings by sound.