Quarantine

Quarantine is a state, period, or place of isolation in which people or animals that have arrived from elsewhere or been exposed to infectious or contagious disease are placed.

This comes from the venitian word "quarantena"  meaning  40 days. Originally when a ship arriving in port was suspected of being infected with a malignant, contagious disease, its cargo and crew were obliged to forego all contact with the shore for a period of around forty days. This term came to be known as period of quarantine.