In the late twenties or early thirties of the 20th century, it appeared as a simplification of ㄮ(ē), writing the dot and the second stoke of the bottom part ㄛ(ō) with one stroke. ㄮ(ē) was itself derived from ㄛ(ō) in 1920, when a new allophone appeared, writing a dot to differentiate between them. The letter ㄛ(ō) is itself derived from 𠀀, inhalation, the reverse of 丂(kǎo) and an ancient form of 呵 (Mandarin: hē).
Derived from ㄛ(ō)(Mandarin: ō), which was derived from 𠀀, inhalation, the reverse of 丂(kǎo) and an ancient form of 呵 (Mandarin: hē), because Mandarin: ē is its allophone in Standard Chinese.