How to read the band →
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).
Isaac
Isaac has been easing down from its peak but is still widely used. All-time it's been given to 370,071 U.S. babies, the 75th most common name by sound today, peaking at 11,653 in 2007, with 6,376 in 2025.
By sound, Isaac also includes the spellings Issac, Isaak, Isac, Izaak, Izaac.
Rising