Mysteries of vernacular:
Quarantine,
a state, period, or place of strict isolation
meant to prevent the spread of disease.
In the 14th century,
the Bubonic Plague,
later called "The Black Death,"
spread across Europe
with devastating consequences.
It's been estimated
that the Plague decimated at least one-third
of Europe's population.
In a vain effort to stave off infection,
the Italian-speaking port city of Ragusa,
in what is now Croatia,
mandated that ships arriving
from Plague-infested areas
remain isolated on the water
until it was deemed likely
that they weren't carrying a disease.
This meant that the enter contents of a ship
and all of its passengers
were often forced to remain on board
for five or six weeks before being let ashore.
Though the drastic measure
was only marginally successful,
it wasn't long before other port cities followed suit.
In 1397, the official period of isolation
imposed on ships and crews
was set at forty days.
Although it did little to protect ports from infection,
the directive stuck.
From the Italian word quaranta,
meaning forty,
this period of stasis was given the name
quarantine.
And by the mid 1600s,
the word quarantine was being used
to describe any place,
period,
or state of isolation,
plague-related or not.