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).
Tammy was a common American name in the 1960s but is rarely given today. It's been given to 424,059 U.S. babies all time and once ranked 127th by sound, peaking at 26,395 in 1963 (down to 59 in 2025).
By sound, Tammy also includes the spellings Tami, Tammie, Tammi, Tamie.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).