During the COVID-19 coronavirus disease pandemic of 2020, many Americans first became acquainted with the phrase “social distancing,” a term referring to the practice of people avoiding gathering in groups and maintaining physical space between themselves in public settings (in order to prevent the spread of COVID-19). The words “isolation” and “quarantine” also saw an increase in usage during the pandemic, but although they are often used synonymously, they have distinctly different meanings, as the Centers for Disease Control and Prevention (CDC) explained on its website: Isolation separates sick people with a contagious disease from people who are not sick. Quarantine separates and restricts the movement of people who were exposed to a contagious disease to see if they become sick. Thus, persons who have contracted COVID-19 and are staying at home in order to avoid spreading the illness to others are properly said to be self-isolating rather than self-quarantining. Nonetheless, the common use of “quarantine” during the pandemic got some people wondering where that word came from, a question one meme attempted to answer:  The explanation offered in this meme is largely correct, although in its brevity it omits some of the more interesting etymological background. The roots of “quarantine” lay in the multiple outbreaks of bubonic plague (popularly known as the “Black Death“) that hit Europe beginning in 1347 and killed an estimated one-third of the population. According to a 2002 article published in the journal Clinical Infectious Diseases, city officials around the Mediterranean seaport of Ragusa mandated in 1377 that persons who sought to enter the city after traveling from plague areas must first remain in isolation for a 30-day period known as a “trentino” (from the Italian word “trenta,” meaning “thirty”):
"The word ""quarantine"" stems from the Italian word for ""forty,"" representing the number of days persons potentially exposed to communicable diseases had to remain in isolation."