It is used by the users over on the chat feature of the streaming platform to express the ultimate pleasure possible to be felt by a human being.
Billy Herrington was already a popular personality on Japanese sites in the early 2000’s with him appearing in mashup videos frequently. The root of the emote’s name comes from the Japanese word; Gachimuchi, which means fat muscular.
This set the foundation for him being widely recognized.
His career on Twitch TV began in 2015, when even Forsen had adopted him, after the GachiGASM meme had spread from reddit.
GachiHYPER, the ultimate edition of the emote was added to FrankerFaceZ by user vopranoS in 2017.
The popularity of deep fried memes is accountable for the creation of GachiHYPER and its obviously perceivable intensity had led it to be widely recognized as the most extreme edition of the Gachi emotes and is currently used across the streaming platform to express feelings of the highest amount of pleasure; an otherworldly sensation during an orgasm… the feeling of DMT being released in the Pineal while nutting must be something like this.