Where does BOS come from?
While it was almost certainly used online prior, a 1999 index of internet acronyms includes BOS as an initialism for boyfriend over shoulder (i.e., my boyfriend is looking over my shoulder), used to signal a lack of privacy and need to be discrete in digital conversations. In this vein, BOS can also stand for boss over shoulder when someone needs to abruptly leave a chat, say, or stop online-shopping at work. Similar over shoulder constructions include GOS (girlfriend over shoulder) and POS (parents over shoulder).
More commonly, BOS is short for the city of Boston. This particular abbreviation may come from the airport code for Boston's Logan International Airport, BOS, a convention starting in the 1930s. BOS is also used as a display name for Boston-area sports teams on television and other sport media (e.g., BOS v. NYY, or the Boston Red Soxs vs. the New York Yankees). We can find BOS used for Boston on Twitter, for example, mere days after the social-media platform launched in 2006.
Who uses BOS?
As a short form of Boston, BOS is widely and commonly used to indicate travel to Boston or for several of Boston's sports team, including the Red Sox (baseball), Celtics (basketball), and Bruins (ice hockey). The familiarity of this abbreviation has lent BOS to merchandise (e.g., I ❤️ BOS shirts). BOS can also refer to the city more generally, especially as a hashtag (e.g., Severe weather coming to #BOS or Training for the marathon #BOS).
As an acronym, BOS may be used in text messages or internet chats when someone needs to communicate slyly. This could be benign, such as a man refraining to text certain details because he is planning a surprise birthday for his boyfriend (talk later BOS) or more nefarious, if, say, a girlfriend has been flirting with a guy who isn't her partner.
Be mindful that many other various organizations may abbreviate their name as BOS, as does the Bank of Scotland, British Overseas School, or Brussels Outdoor School.
Also note that in certain gang cultures, BOS can stand for beating on sight or refer to the Brotherhood of Struggle, a subset of the Chicago-based Black Gangster Disciples street gang.
Oh shit, boss over shoulder. Minimize, minimize, minimize. #bossovershoulder #BOS
@thegirlwho____, May, 2016
Did Morris just fall asleep during the last possession? #NBA #BOS #WAS
@voltixftw, March, 2018
If you love BOS, then its must be the shirt for you. It can be a better gift too.
Cummings, SunFrog (item description), 2015