Siddham letter vocalic rr

It writes Sanskrit’s long syllabic vowel ṝ. “Syllabic r” means the r itself serves as the vowel; the line over r in ṝ marks its long form. 𑖇 is an independent letter, unlike ◌𑖵, which attaches to a consonant.

A terracotta inscription from Sugh preserves an early Brahmi vowel sequence from around the second or first century BCE. As Brahmi adapted to Sanskrit, its vowel series included syllabic ṛ and ṝ; this inscription traces that older tradition, not this exact letter’s origin.

A writing lesson became ritual script

Siddham charts taught learners vowel series and consonant–vowel patterns. Siddhamātr̥kā, the Siddham script tradition, developed from Brahmi, an ancient Indian script; it is related to Sharada and belongs to the line that led to Devanagari and Tibetan.

Across China, Japan, and Korea, Siddham carried Sanskrit Buddhist manuscripts, mantras, and dhāraṇīs (short ritual texts). Japanese Buddhist practice also calls this writing bonji. The Unicode Standard 17.0 describes Japanese Siddham use as chiefly ceremonial in Shingon and Tendai Buddhism.