Looking at urban dictionary, I noticed the word SWAG. Now, I worked for Corporate America for a couple of decades and to me, the acronym has always declined into Stupid Wild-Assed Guess. However, on the street these days it means Secretly We Are Gay. I guess I can’t register the damned thing, but somehow I’m affronted.
No, no, it means Stuff We All Get. Free stuff, like from radio promotions, drug reps in doctors offices, etc.
I doubt it’s an acronym- these things usually aren’t. Here’s a Snopes entry about it, and I found one dictionary that cites its origin as “Middle English (in the sense ‘bulging bag’): probably of Scandinavian origin. The original sense of the verb (early 16th cent.) was ‘cause to sway or sag.’”
In the Navy we always called it a Scientific Wild Ass Guess. Adds to the credibility. 
Swag from The Online Etymological Dictionary which is generally quite good linguistically speaking with the unfortunate exception of the entry for literally.
The most modern usage means either material gained for free, often as part of a promotion or one’s self-confidence and bravado. Secretly We Are Gay and Stuff We All Get are backronyms, created as an attempt in the former to insult a group of people the speaker dislikes who use that slang among themselves and in the latter as an attempt to logically explain the association between the word and its meaning.
You’ve heard of people walking around with a swagger in their step? It’s because they’re loaded down with a bunch of free stuff.
I bet even my mom knows what swag is. You guys need to keep up.
I thought it was a type of lamp.
If you have to ask, then you ain’t got it.
“Swag” has made a bit of a comeback recently. It’s a popular internet meme and was popular in high schools 2 years ago. This time around, it means to dress or act in a cool, eye-catching way. It came into fashion around the same time as YOLO.
So now you know. You can all go back to being old.
Yup. The stuff we scammed at the vendors fair at conferences. Pens, magnets etc. my kids now hate it when I call it swag.
Been calling it that for over 20 years.
Related example: swagman, as in:
See now we call “SWAG” a SUPER wild ass guess, as opposed to a simple, garden variety Wild-ass guess (WAG.)
Here’s a thread about it:
It wasn’t created as an acronym. Fairly recently it began to be used by young people to mean something “neat, cool, hip.” Other people were annoyed by this word, and they made up a joke that it really meant “Secretly we are gay.”
The first time I heard it used was in pharmacy school, and it was used this eay too. Scientific Wild Ass Guess.
Sealed With A…Grope?
I always thought swag was pirate booty and by modern-day extension any sort of loot, which could also include free stuff.
Sealed With A Grape. 
AcronymFinder.com lists 84 meanings for SWAG. I particularly like Satan’s Wishes Are Granted, Sex with a Goat and Sleeping with a Ginger.