It is generally believed that the word "Meng" comes from "Shao" and from Japanese IME input method. The original meaning of "Meng" refers to the emotional state of readers when they see the role of a beautiful girl. Hot-blooded works often use "burning" to describe this state. If you use Roman Pinyin, it is "Mo E (もぇ)". If you use Japanese input method, only "burning" and "Meng" will be displayed when you input Mo E. In order to distinguish the state of blood boiling because of beautiful girls from the traditional state of blood boiling, the homonym "Meng" is used to describe it, which has also become an online slang in ACGN.
There is also a saying related to the meaning of Chinese characters. According to the dictionary of business students, "Meng" refers to the germination of plants and trees, which is a metaphor for the beginning of things, so it may also be taken as an extension of "starting to attract attention". It is also said that when you see a beautiful girl, you feel that spring has arrived and the grass sprouts in spring, so you borrow it to represent this "be elated" state.
According to the Japanese model dictionary, there are other versions of the origin of Meng.
One of them is the heroine "Sakize. Meng in the TV King of Genius broadcast by NHK on 1993 will call her name Meng ~! There are fans imitating. Another view is that there is a TOMOE firefly in the TV animation "Girl Warrior S", but there is no definite view at present, so the two expressions of "burning" and "budding" have become the most accepted views at present.
There are always different opinions about the origin of "Meng". But at present, the systematic development of Meng is considered to have a very direct relationship with love games (commonly known as "Gal games" or "women's games").