Phags-pa Letter Dda

It writes Sanskrit ḍa, a d sound with the tongue curled back.

The Phags-pa script was modeled chiefly on Tibetan, but its letters are written in top-to-bottom columns, a direction associated with Mongolian. ꡫ is the mirrored counterpart of ordinary Phags-pa da ꡊ, added for Sanskrit's retroflex series.

At the request of Mongol ruler Kublai Khan, Tibetan Buddhist teacher Drogön Chögyal Phagpa devised the script to write Mongolian and the empire's other languages in one system. The earliest known Phags-pa writing on a Chinese monument dates to 1269; that dates a surviving example, not the first proven use of this particular letter. The script served administration and appeared on inscriptions, seals, coins, and banknotes, as well as in books and Buddhist texts, but never replaced the older Mongolian script. After the Yuan fell in 1368, use in China and Mongolia largely stopped; it persisted in Tibet for limited purposes. By the late sixteenth century, a decorative Tibetan form called hor-yig (“Mongolian writing” in Tibetan) appeared on seals, book covers, and buildings. Its seal style echoed Chinese seal script.

Why does Phags-pa Dda flip the next letter?

Some following letters mirror to continue ꡫ’s vertical stroke.

When ꡫ begins a Sanskrit syllable, Phags-pa shaping can mirror certain following glyphs so their strokes join along the same vertical line. The sequences ꡫꡜ and ꡫꡠ are the Sanskrit transliterations ddha and dde. The sequence remains the same two letters; only a following glyph's displayed shape changes.