This is a word commonly used within small male tribes. When one male of a tribe begins spending time with an female interest instead of his tribe, the other males of the tribe will become jealous and angry, causing them to lash out by calling the drifting male a "simp" in an attempt to shame him into spending more time with the tribe and less with the female interest.
Tribe: "Kevin, how dare you spend time with someone other than us."
Kevin: "I genuinely enjoy spending time with her. Sue me."
Tribe: "This wamen will slowly suck your soul dry and you'll eventually never be allowed to do the only thing you love, playing videogames with us, ever again. Wamen are dumb. Quit being such a simp."
Kevin: "I'm barely online anyways."
Tribe: "Why do you even like this girl? Do you respec wamen or something? Pfff simp. Go ahead. Go be a little simp."
Kevin: "Okay." *leaves*