See also: 大
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 by adding a stroke to ㅈ (j, “j”) to represent aspiration.
ㅊ • (ch)
- ㅊ (chieut) is pronounced as an aspirated alveolo-palatal affricate ([t͡ɕʰ]), i.e. similar to the English ch.