Yippie Ky Yay Mother F**** originated in the movie "Die Hard".
A police officer was trapped in a building while on vacation, and the building was taken hostage. He got away and fought back. In a few scenes the officer runs into range of fire of the terrorists, and yells "Yippie Ky Yay Mother F*****!".
Being such an odd sentence, people all over the internet have made memes of the line, and the memes are continuously used.
They are used for YOLO moments, and just randomly used.
Another version of this meme is "Yippee Ki Yay Mother Buttcheeks".