Why does seme called seme?

Then uke are uke cause they're like ukulele. You know you've to use "fingers" and all...

Why you so extra

╮(￣▽￣")╭ (why asking questions I don't know the answers?!?)

All your answers are here: https://www.japanesewithanime.com/2017/09/seme-uke-meaning.html?m=1