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.
Choe Manri
Choe Manri (?-1445, sometimes spelled Choi Malli) was an associate professor in the Hall of Worthies (집현전 부제학, 集賢殿副提學) who spoke against the creation of "hangul" (then called "eonmun") together with other Confucian scholars in 1444. He made the following submission that year to King Sejong against "hangul":