Hangul Day
Before the creation of Hangul, people in Korea (known as Joseon at the time) primarily wrote using Classical Chinese alongside native phonetic writing systems that predate Hangul by hundreds of years, including idu, hyangchal, gugyeol, and gakpil. However, due to the fundamental differences between the Korean and Chinese languages, and the large number of characters needed to be learned, there was much difficulty in learning how to write using Chinese characters for the lower classes, who often didn't have the privilege of education. To assuage this problem, King Sejong created the unique alphabet known as Hangul to promote literacy among the common people.
Origin of Hangul
Another letter composed of two elements to represent two regional pronunciations, now obsolete, was ㅱ, which transcribed the Chinese initial 微. This represented either "m" or "w" in various Chinese dialects, and was composed of ㅁ plus ㅇ. In ’Phags-pa, a loop under a letter, ꡧ, represented after vowels, and Ledyard proposes this rather than the null symbol was the source of the loop at the bottom, so that the two components of ㅱ reflected its two pronunciations just as the two components of ㆁ "ng" did. The reason for suspecting that this derives from ’Phags-pa ꡧ "w" is that the entire labio-dental series of both ’Phags-pa and the Korean alphabet6, used to transcribe the Chinese initials 微非敷 "w, v, f," have such composite forms, though in the case of ’Phags-pa these are all based on the letter ꡜ "h" (ꡤ "etc."), while in Hangul, which does not have an "h" among its basic consonants, they are based on the labial series ㅁ "m," ㅂ "b," ㅍ "p."