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
Ju Si-gyeong, the linguist who had coined the term Hangul to replace "Eonmun" or "Vulgar Script" in 1912, established the Korean Language Research Society (later renamed the Hangul Society), which further reformed orthography with "Standardized System of Hangul" in 1933. The principal change was to make the Korean alphabet as morphophonemically practical given the existing letters. A system for transliterating foreign orthographies was published in 1940.