There are dozens of phrases in our daily slang that come from military language, but many people don’t even know it. ‘Watch your six’ is one such phrase that has migrated into our everyday language from military slang. And there it had a very specific meaning.
What does it mean to “watch your six?
It is one of the military terms. As you may know, the military divides directions into chapters. There are twelve in all, just like on a clock. If conventionally 12 is in front, then six is in the back. It means (quite logically) watch your back. The term is also used by the police as well and with the same meaning.
Where it came from?
It originated during World War I, when fighter pilots referred to the back of their aircraft as their six and later evolved to be used everywhere in combat; for example: “Watch my six” or “I’ve got your six” means “Watch my back” or “I’ve got your back” respectively.