Here lies the humble beginnings of L.E.T. from the memoirs of Dr. Thomas Gordon. He was a flight instructor (Aircraft? B-24 Mitchell for those who are curious) for the Army Air Corps during WWII. He describes an experience that really opened his eyes about how leaders can dramatically impact the performance and morale of their subordinates—or in this case, students:
“Our main purpose was to influence flight instructors to drop the conventional authoritarian ‘tough guy’ role that usually instilled so much fear and tension that students didn’t perform well.
We wanted to avoid unnecessarily high rates of wash-outs [failures]. In this job, I had a leadership position for the first time. Heading a group of 
six fellow officers, I fell into the trap of ‘taking charge.’
I set the main goals myself—after all, I thought I was more expert—assigned the tasks, and assumed sole responsibility for evaluating progress.
Certainly, I did little to dispel the notion that I was the boss and the group members were my subordinates.
To my surprise and puzzlement, within a few months morale was bad, resistance was high, production was low, creativity was nil, and open and honest communication ceased between the group members and me.
Fortunately, thanks to the honesty of one of the officers, who was also a close friend, I was able to see the destructive effects of my authoritarian leadership soon enough to make a complete turnaround.
I began to invite full participation of group members, listen to their ideas and feelings, and transfer ownership of the project and responsibility for group governance to the group itself.
This changed leadership style had startling and enduring effects: creativity flourished, communication opened up, tension decreased, and the work became enjoyable and satisfying to all of us.
A sick group became a healthy one, and the project became fun.” ∎
And so that, my friends, marked the beginning of what has become L.E.T.!