It's a phrase we've all heard before, but what does it really mean? Most people probably shrug and guess it's a synonym for "son of a b-word," but it actually has a very specific historical context.
In the 1600s and 1700s, when the British Navy was in its hayday, there were a lot of cannons and muskets being fired, and a lot of sailors lost their fathers on the job. As you might imagine, this often left children as young as 10 to fend for themselves.
The orphanages and poorhouses for kids at the time were a bit rough and tumble, so that's where the phrase "son of a gun" came from. "Son" just means "orphan," and "gun" refers to the navy. So there you have it — someone who doesn't have any parents.
Usage-wise, this phrase doesn't have quite the bite that "son of a b-word" does, but it was often used as an insult meant to deprecate someone's lower birth status and rough upbringing.
In today's society, you don't hear "son of a gun" much, but it's still a fun one to whip out when you want to tease a bit. Just remember that it's not really as mean as it sounds!
So that's the story of "son of a gun." Who knew that orphanages and the British Navy had so much to do with the way we talk today? Now you can impress anyone you meet with your newfound knowledge. Just be sure to use it for good and not for evil.