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).
Martin
Martin is now well below its former popularity. All-time it's been given to 317,037 U.S. babies, the 623rd most common name by sound today, peaking at 6,091 in 1963, with 1,009 in 2025.
Martin has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).