Swagger. What does it really mean?

According to http://www.merriam-webster.com,

²swag·ger

noun \ˈswa-gər\

Definition of SWAGGER

1

a : an arrogantly self-confident way of walking : an act or instance of swaggering

b : arrogant or conceitedly self-assured behavior

c : ostentatious display or bravado

2

: a self-confident outlook : cockiness

I've first encountered that word from a song. It's supposed to be used by maangas people, like those rappers who sing about it. Kids from Tumblr and Twitter seem to be using the word differently, though.

I've seen people in my Twitter timeline write "Just brushed my teeth. #SWAG". How is that swag, right? These kids don't know what the word really means but use it just to look cool. Which kinda sucks.

I'm not annoyed because they're trying to sound cool. I am annoyed because kids nowadays say things without knowing/understanding their real meaning. And since I am a mom now, I am also becoming paranoid because I have a daughter who might sprinkle the F word in her sentences like there's nothing wrong with it (I WAS guilty of this). It's my job to make Brianna understand but whose job is it to make the other kids understand?