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).
Amber was more common in the past and has since settled at a lower, steady level. All-time it's been given to 378,699 U.S. babies, the 907th most common name by sound today, peaking at 17,061 in 1986, with 684 in 2025.
By sound, Amber also includes the spellings Ambar.