It's actually the name of a very bad newer song. But when people say "moves like Jagger" or "smooth like Jagger"(Mick Jagger), they're are trying to say you're slick/smooth/cool/alot of confidence but not arrogent, you know how to talk to the ladies by saying and doing all the right things for them to like you, etc.... And I'm guessing "swagger" comes from the new made up word that the younger generation is starting to use alot more. "Swag" is a new word to me, that I never heard of until about a year ago when a younger girl(19) told me she liked my swag. I'm 33, I never heard of the word before, but I acted like I knew what she said. And by her actions I knew what she meant. So "swag" is basically defining how your approach is with the girls/ladies, your confidence in talking to the ladies, the way you walk/the way you carry yourself when your around others, etc... each generation seems like they come out with their own words/slangs, and even some of the words may have been used a long time ago, and each new generation brings back a few of them words/slang words that have been forgotten about for years. And sorry my opinion of defining these words, says how you act and carry your confidence around women, It's the same definition for how women act and carry themselves too. I think the word "swag" is just another word for the word "swass" that was actually made into a rap/r&b song back in the early 90's by a group called "sir-mix-alot", the song was called Swass (don't you wish your boyfriend was swass like me)... But if you wanted to interpret your own opinion of the definitions, then I'd suggest you check out the songs : "Swass by- sir-mix-alot", "Moves like Jagger by- maroon 5" and "Swagger Jagger- by cher lloyd", but I'll warn you, they are all terrible songs haha :) Hope this helped you understand the words a little better.

Swagger is used to describe the way someone moves, we use it in Australia often to describe the way someone walks as in "Walk or behave in a very confident and typically arrogant or aggressive way: "he swaggered along the corridor". Swagger Jagger comes from the Cher Loyd song, and is apparently misuse of the term Swagger Jacker - someone who copies or steals another person's style. I'd hesitate a guess that this isn't a common phrase anywhere...

swagger = Brit informal, rare elegantly fashionable jagger = from Mick Jagger, the Rolling Stone who had a lot of swagger!