Ships arriving in Venice from infected ports were required to sit at anchor for 40 days before landing. This practice, called quarantine, was derived from the Italian words quaranta giorni which means 40 days.
The Italian words quaranta giorni meaning "40 days" gave origin to quarantine. To protect coastal cities from plague epidemics, this practice began during the fourteenth century. Ships arriving from infected ports to Venice were bound to sit at anchor for 40 days as a quarantine measure.
The Black Death annihilated about 30% of Europe's population along with a significant percentage of Asia's population between 1348 and 1359. Newcomers entering the city had to spend 30 days (a trentine) in an isolated place (nearby islands) waiting to see if the symptoms of Black Death would appear, as stated in the original document from 1377 kept in the Archives of Dubrovnik. Later on, it was prolonged to 40 days, changing the term from "trentine" (30 days) to "quarantine" (40 days).