humour

Where it comes from

Humour ordinarily means the quality of being funny, or the ability to notice and express amusement. Humour came through French from Latin humor or umor, moisture or bodily fluid. Ancient and medieval medicine treated blood, phlegm, yellow bile, and black bile as four humours whose balance was thought to shape health and temperament. Because a person's mixture of fluids supposedly governed disposition, humour came to mean temperament and then a passing mood or whim.

How the meaning developed

From an odd disposition or caprice it developed senses involving comic character, the perception of incongruity, and funniness.