Dour
Etymology
Probably from Latin durus, "hard," which also gives us "durable" and "endure." It entered English through Scots, where it long described hard, forbidding people and hard, forbidding places alike. The sense of grim, unyielding hardness of temperament is a direct extension of that original "hard."
adjective · /DOOR/
Relentlessly stern, gloomy, and unsmiling in manner.
What it names
The specific joylessness of someone whose severity feels like a fixed weather system rather than a passing mood.
Example
The dour headmaster met every joke with the same flat, disappointed stare.
Related idea
Morose is sunk in gloom and self-pity; dour is harder and colder — stern and forbidding rather than merely sad.