When someone is all up in your "kool-aid" either by accident or on purpose. When someone is too close for your particular comfort.
While you are working on your PC and some guy comes up looking over your shoulder and his junk bangs into your shoulder. Or maybe a barber leans too close while you are under the shroud in a barbers chair, "junking" your arm or elbow that is rested on the barbers chair arm rest. You would at this point exclaim, "How 'bout hangin' back, ya jammin' my frequencies!"