A harness(notice the lack of a 'd') is a strap system to gain control over something.
Like the thing people attach a dog lead to so that their kids won't just go kamikaze into a car.
Coding harnesses are named by analogy to that.
They are not hard.
The reason I have a dog harness is to distributes weight so I don't choke her when she goes at the other dog that she doesn't like. I'm actually puzzling over kids kamikazeing into cars
You got to miss spell these days or people assume your ai :)