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).
Judith was more common in the past and has since settled at a lower, steady level. All-time it's been given to 455,955 U.S. babies, the 1,400th most common name by sound today, peaking at 25,303 in 1943, with 344 in 2025.
Judith has no common alternate spellings by sound.