temper

Where it comes from

Temper ordinarily means a person’s state of mind or anger; as a verb, to moderate or strengthen by controlled treatment. Temper comes from Latin temperare, to moderate, restrain, mix to a proper strength, or maintain in balance. Its possible deeper relationship to tempus, time or measure, is debated and should not be stated as certain. A well-tempered mixture had its elements in suitable proportion.

How the meaning developed

The idea extended to metals brought to desired hardness, music tuned into a system, the balanced disposition called a temper, and finally the angry temper that can flare or be lost.