Quarantine does not accurately describe what the WHO is asking people to do. Quarantine is when you take potentially infected people and isolate them from the rest of the population, allowing all the unexposed people to go about their days normally.
Edit: Updated to clarify that quarantine is about potential and not actual infection.
No, quarantine is when you isolate a group of people for a period of time. It is used to see if they MIGHT be sick, or when people are known to be sick, to allow it to burn out.
The original usage was specifically when ships were required to stay in port for 40 days before being allowed to dock, so that any sickness could burn itself out or be apparent.
Thanks for the correction. You're right that quarantine does not require knowing whether people are actually infected. However, it's still about isolating specific people or things to protect the rest of the population and not about asking the whole population to change its behavior.
The Wikipedia article for cordon sanitaire [1] mentions quarantine as an alternative way to handle disease spread.
> Public health specialists have included cordon sanitaire along with quarantine and medical isolation as "nonpharmaceutical interventions" designed to prevent the transmission of microbial pathogens through social distancing.
Edit: Updated to clarify that quarantine is about potential and not actual infection.