The backs of your calves, typically if you are lacking in muscle mass and they are quite 'dangly'.
In addition, if the backs of your thighs are also quite dangly, you may refer to these as your 'upper pholofolous'.
Check out my pholofolous; they are jigglin' off the hook!
Person 1: 'check out my pholofolous!'
Person 2: 'dude, you gotta hit the gym or some stairs or something!!'