Literally meaning ‘40 days’, quarantine comes from Italian quarantina, from quaranta ‘40’. In the early 16th century this was the number of days during which a widow had the right to remain in her deceased husband's house. A more familiar meaning refers to a period of isolation imposed on a person or animal to test that they are not carrying a contagious disease. This was first used in English in the mid 17th century, though the practice dates back to the 14th century, when the ports of Venice and Ragusa (now Dubrovnik) required ships from plague-stricken countries to lie at anchor for 40 days before they were allowed to enter the ports.
14世纪中期，一场毁灭性的瘟疫在欧洲蔓延，这就是所谓的黑死病（Black Death）。它于1346年首先出现在黑海地区，然后沿西南方向向地中海传播，并在随后几年内蔓延至整个欧洲，毁灭了欧洲将近三分之一的人口。
1347年，威尼斯启动一项措施，强制要求所有来自疫区的船只在港口外停泊40天后才允许靠岸。这段隔离期在意大利语中被称为 quarantina giorni （space of forty days）。其中， quarantina 源自 quaranta （40），意思就是“40左右”。
后来，人们就逐渐开始用 period of quarantine 表示任何期限的隔离期，而 quarantine 也就成了“隔离”的代名词，既作名词表示“隔离、隔离期、隔离区”，也作动词表示“（对动物或人）进行检疫、隔离”。