An experiment was conducted - five monkeys in a cage, bananas hanging on the top, ladder welcoming their attempts to grab juicy fruit. Surprisingly (for monkeys only, since that was the purpose of experiment) each time any of them would try to take banana water would spray all over the cage and, of course, monkeys didn't like that at all. After few attempts all five monkeys rested and ignored forbidden fruit.
This experiment wouldn't be interesting if it stopped here - the next step was to remove one of the monkeys and place a new monkey in the cage. Revelation! New monkey went straight for bananas while old monkeys panicked, blocking the way up the ladder. One by one they removed old monkeys and placed new ones in - nobody got sprayed but somehow nobody was daring to go up the ladder either.
That is how the term learned helplessness came to existance.
Hold your breath, similar experiment was done with humans (instead of being sprayed by water loud noise was the 'punishment' and, voila, same thing happened).