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 is down from its peak but still widely used. All-time it's been given to 364,337 U.S. babies, the 74th most common name by sound today, peaking at 11,413 in 2007, with 6,291 in 2025.
By sound, Isaac also includes the spellings Issac, Isaak, Isac.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).