Where did the term "don't fly off the handle" originate?

Answer 1

Meaning

Lose self control.

Origin

This is an American phrase and it alludes to the uncontrolled way a loose axe-head flies off from its handle. It is first found in print in Thomas C. Haliburton's The Attaché; or, Sam Slick in England, 1843/4:

"He flies right off the handle for nothing."

Haliburton was an inventive writer and had a hand in the coining of several commonly used phrases:

Ginger up
Won't take no for an answer
Fly off the handle
Over the moon

Answer 2

Fly off the handle -
If you've ever seen a person 'fly off the handle,' you may have been impressed at the energy and speed involved with that eruption of anger.
Frontiersmen found it hard to control their tempers when tools suddenly failed them.
A common cause of such a turn of events was the shrinkage of wood - universally used to tool handles.
After having hung in a shed for months, the handle of a hoe or a rake was likely to come off after a few strokes.
In the case of an ax, badly worn or shrunken wood is positively dangerous because the head of the tool can come loose at the first lick.
When the blade of an ax flies off the handle, it endangers the user and everyone standing nearby.
That makes it almost as great a source of danger as a violent explosion of temper.