Origin of Hangul
Ledyard holds that the Koreans adopted five core consonant letters from ’Phags-pa, namely ㄱ "g" , ㄷ "d" , ㅂ "b" , ㅈ "j" , and ㄹ "l" . These were the consonants basic to Chinese phonology, rather than the graphically simplest letters (ㄱ "g" , ㄴ "n" , ㅁ "m" , and ㅅ "s" ) taken as the starting point by the "Haerye." A sixth letter, the null initial ㅇ, was invented by Sejong. The rest of the consonants were developed through featural derivation from these six, essentially as described in the "Haerye"; a resemblance to speech organs was an additional motivating factor in selecting the shapes of both the basic letters and their derivatives.
Hangul
The explanation of the letter "ng" also differs from the traditional account. Many Chinese words began with "ng", but by King Sejong's day, initial "ng" was either silent or pronounced in China, and was silent when these words were borrowed into Korean. Also, the expected shape of "ng" (the short vertical line left by removing the top stroke of ) would have looked almost identical to the vowel . Sejong's solution solved both problems: The vertical stroke left from was added to the null symbol to create (a circle with a vertical line on top), iconically capturing both the pronunciation in the middle or end of a word, and the usual silence at the beginning. (The graphic distinction between null and "ng" was eventually lost.)