Social distancing has traditionally been a technical term refering to many different methods of keeping people apart. Until very recently -- early March, 2020 -- the stay six feet a way from other people rule was not a particularly emphasized part of social distancing.
Documents on managing the spread of infectious disease tend to provide lists of key components of social distancing that look something like this:
- Isolation of cases
- Quarantine of contacts
- Stay-at-home recommendations
There is significant breakdown of those categories, of course, but it is an umbrella term, not a specific recommendation. The term is both an accurate description of what is being recommended and surprisingly slippery. The CDC report on recommendations for managing flu outbreaks published in 2017 (link) included things like telecommuting, school closure and cancelling mass gatherings, but when it came down to listing their specific recommendations they gave two examples: maintaining at least 3 feet between individuals, and voluntary home isolation of those infected.
The current recommendations for social distancing remain much the same as the ones for influenza, which unfortunately means that most of them are not tailored for COVID-19. Specifically, the six-foot recommendation seems to be based entirely on studies of influenza (like this one) that document a reduction of infection as distance increases; it is not clear that this is appropriate to the coronavirus specifically, and it is absolutely not okay that people are treating at as a golden rule in distancing beds in hospitals and homeless shelters. However, as it is an estimate of the furthest distance that droplets from coughs and sneezes will usually travel, and because it is easy to remember, it is a useful Schelling point.
The messy terminology leads to possible misunderstandings and manipulations. Social distancing recommendations from various reports include things like liberal leave policies, cancelling school, avoiding groups of 10 or more, and, of course, maintaining 6 feet or 2 meters from other people. The government and the media are going to focus on easy, free, and simple to communicate solutions like keeping your distance from your friends; this is only one aspect of social distancing, and was, until this month, a comparatively minor one.