I. quaranta = forty.
Refers to the practice established in European port cities during the Black Death requiring vessels to lie at anchor for 40 days before landing. Isolation (from the Latin insula or island), the practice of separating sick persons from those who are healthy to prevent spread of disease, goes back a long time. “As long as they have the disease they remain unclean. They must live alone; they must live outside the camp” (Leviticus 13:46).
Quarantine, on the other hand, is the practice of separating persons who appear to be healthy but mayhave been exposed to a disease. In 1377, the Great Council of Ragusa (modern-day Dubrovnik) establisheda 30-day separation period (trentino) for visitors from plague-endemic areas. In the following decades, thepractice spread to other cities and was extended from30 to 40 days (quarantino). The longer period may have been more effective at preventing disease or just a nod to the 40-day duration of Biblical events–the Great Flood or Jesus’ fast in the wilderness.
Sources & copyright: https://wwwnc.cdc.gov/eid/article/19/2/pdfs/et-1902.pdf