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).
Arjun has held a fairly steady level of use. All-time it's been given to 12,176 U.S. babies, the 1,043rd most common name by sound today, peaking at 650 in 2014, with 615 in 2025.
Arjun has no common alternate spellings by sound.