What is Shake It Off?
1.
To forget about someone or something, to let go, to get over it, to move on.
As in Mariah Carey's song:
"I gotta shake it off
Cause the loving ain’t the same
And you keep on playing games
Like you know I’m here to stay
I gotta shake it off
Just like the Calgon commercial
I really gotta get up outta here
And go somewhere
I gotta shake it off
Gotta make that move
Find somebody who
Appreciates all the love I give
Boy I gotta shake you off
Gotta do what’s best for me
Baby and that means I gotta
Shake it off"
See
2.
After a male urinates, he doesn't wipe like a female would. Instead he holds onto his genitalia and "shakes" it, so as to dry off.
He had to (shake it off) so he could put it in his pants.
*glancing around stupidly at your friends, miming the shaking off* "(SHAKE IT OFF)".
~(shake it off) can also be used as a dumb immature joke, as seen in example number 2~
