In Japanese the phrase is an idiom used to mean "get angry." is a slang version of that that emphasizes just how cheesed off you are. (=) is the red part at the top of a chicken/rooster's head. Notice how it goes up through the head and kind of flares out. Because of how silly the image is, though, you'd use it at a time when a kind of silly playfulness is involved. According to this site it might refer to the redness of the chicken as blood rushing to your head.
Apparently when you're seriously angry and just _have_ to express it through a bodily extremity, you can use {}{}.