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).
Briar has been climbing in recent years. All-time it's been given to 13,349 U.S. babies, the 658th most common name by sound today, peaking at 1,175 in 2025, with 1,175 in 2025.
Briar has no common alternate spellings by sound.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).