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).
Darrell was more common in the past and has since settled at a lower, steady level. All-time it's been given to 360,001 U.S. babies, the 1,267th most common name by sound today, peaking at 11,941 in 1961, with 383 in 2025.
By sound, Darrell also includes the spellings Darryl, Daryl, Darrel, Darell, Daryle.