MonkaW can be used to express tension, for example when the streamer is playing a horror game on screen and a scary part is up.
It is part of the FrankerFaceZ, which is an extension to your browser to enhance your viewing experience, by having access to new features like emoticons and chat functions etc.
MonkaW is part of the MonkaS variant emotes which are as following:
Origin of the emote
The unique emote for MonkaW was added the streaming website Twitch.tv and to the browser extension called FrankerFaceZ on 2017.
Spread of the emote
As of 10/12/2019 according to the website StreamElements, MonkaW is the 16th on the list of most popular/used emotes on the streaming website Twitch.tv, making it one of the most popular variants of the original emote FeelsGoodMan, which both feature Pepe the Frog.