The term described by the little finger being wiggled is 'needledick', indicating the insultee has smaller than desired sexual equipment. The smaller the wiggle, the smaller the equipment. This is echoed in the 'dickhead' gesture of making an O with the thumb and fingers of one hand, raising them to your forehead and making in and out movements.... the smaller the O, using just the thumb and forefinger as if indication a small amount, the smaller the equipment...

LTS