I think it comes from the days of the Black Plague.
The city's population of 3000 dropped about 40% due to the Black Plague and several wars around 1350.
During the "Black Plague", a third of the population died.
It turns out that he became sick with the Black Plague during the night.
Who has said any of those things about the Black Plague?
They were struck with the Black Plague and forced to retreat, although not until the following year.
With it upon you, you need not fear even the Black Plague.
In 1720, 13,000 people (half the population) died of the Black Plague.
The Black Plague was still with us, rising every ten years or so to claim victims.
"Sometimes what seems evil turns out good, like the Black Plague."