See also:𠃊 [U+200CA CJK UNIFIED IDEOGRAPH-200CA], ㆹ [U+31B9 BOPOMOFO LETTER LH], L [U+004C LATIN CAPITAL LETTER L], ℓ [U+2113 SCRIPT SMALL L], andო [U+10DD GEORGIAN LETTER ON]
The Hunmin Jeongeum Haerye, the treatise introducing the principles behind the Korean alphabet written by its inventor King Sejong in 1446, explains that this glyph was derived from the "outline of the tongue touching the upper palate" (presumably in profile of a person facing left), reflecting the coronal nature of the consonant /n/. According to Sejong, the letters ㄷ (d, “d”) and ㅌ (t, “t”) were created by adding strokes to ㄴ, because all three are coronal sounds.
Gari Ledyard proposes that Sejong derived ㄴ from the lower part of ㄷ, which he believes was itself inspired by the 'Phags-pa letterꡊ(t). Ledyard gives evidence that that Sejong was inspired by 'Phags-pa for the basic glyph forms, although he changed the shapes of the letters drastically in order to enhance the simplicity and rationality of his script, and the ultimate shape of the letters may indeed have been influenced by that of the speech organs (Ledyard 1997).
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