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).
Jack
Jack is down from its peak but still widely used. All-time it's been given to 766,990 U.S. babies, the 36th most common name by sound today, peaking at 12,934 in 1927, with 8,764 in 2025.
By sound, Jack also includes the spellings Jacque.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).