et me start with 2nd part of the question.
Who invented hitting Backhand with both hands? Well, I actually
think that the right question should be: “Who invented One-Handed-Backhand?”!
Have you ever wondered why baseball players or golfers hit with both hands?
Why not to hit with one?
When I tried to hit with a baseball bat, I was already tennis coach.
I always played backhand with one hand. It was so awkward
to hit with both hands and golf and baseball because I got used to do
hitting motion with one hand.
As a tennis coach, in 35 years, I have had thousands of students of all
ages and 80% of kids (U13) and adult women would automatically grab the racket
with both hands and get into baseball stance ready-to-hit, when I told them
that i would through the ball on their left side. I am talking about the beginners.
On the other side, more than 80% of adult men returned balls using one hand.
It is also natural as throwing frisbee..
That is all very natural and it would be very strange if kids and adults would
do the opposite.
Grown up people are not used to do hitting and throwing motion with 2 hands.
Of course they will have the impulse to hit backhand with one hand, as well as kids
and majority of women would do it with both.
Two handed backhand is very natural and convenient bio mechanism. Even a forehand
to hit with both hands is not unnatural at all. Just look at Monika Seles and Santoro
how magical they were playing using both hands in both sides.
So, nobody invented it and also anyone invented it.
If you ask who was the first known player to use both hand, then you could ask Google.
Chris Evert, Connors and Borg are not the first but in our era they are the most known
and they were all amazing. Somebody must taught them.
The first part of the question, how to hit, could be answered with two short explanations:
1. One of two ways is to imagine you want to hit forehand with left hand (lets say you
are right handed).
Hold the handle higher and make the room for the right. Hit lefty forehand and right will
be huge help but consider the right hand as non dominant.
2. Other way is to take baseball position but from the opposite, left side.
Before you hit,you can extend your both elbows or not. It depends of the
teacher’s “school”.Two handed backhand has big advantage against the one
handed: using both hands you are able to create the “lever mechanism”,
so with that way even very weak arms can easily hit/return heavy ball.