The word "quarantine" from Italian “quaranta” means Forty, it appeared in the 14th century in Venice.
It was the main port connecting Europe and Asia.
There is a version that a ship with goods arrived from China to Venice.
When the ship was unloaded, the rats descended and on the their wool was a plague virus, which squandered half of Europe.
After that, all merchant ships should be stand for 40 days on the island of Lazaretto, 4 km from Venice. On 41th day, an inspection commission of doctors was on board. If there were no problems, the ship could moor in St. Mark's Bay, and if problems were identified -
The dead were buried in the Lazaretto island.
Theoretically, Venetian doctors were supposed to treat the sick sailors, but in practice, the fear of the disease prevailed over the Hippocratic oath.