Interesting thing I learned today - duct tape can be refered to as duck tape. Here's why-
As with many things duct or duck tape originated in the military (much like WD-40) anyways because soldiers found it so useful in wet and dry conditions and because water beads on its back (like rain off a duck) they lovingly refered to it as duck tape - later it proved useful in many situations - and became also known as duct tape