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).
Ruby is down from its peak but still widely used. All-time it's been given to 401,033 U.S. babies, the 191st most common name by sound today, peaking at 8,819 in 1924, with 3,830 in 2025.
By sound, Ruby also includes the spellings Rubi, Rubye, Rubie.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).