Actually, duck tape and duct tape are two different products.
Duck tape is waterproof cloth reinforced tape that was originally invented by the navy. Most people think that it's silver, but the real color is battleship gray. That's because it is used on ships.
Duct tape is silver in color. It's manufactured by applying a wind proof adhesive to a thin sheet of aluminum metal. It is used to install furnace ductwork.
Duck is now a brand name for duck tape. Duck brand duck tape comes in a variety of colors.
So when I recommend duck tape, I'm talking about duck tape, not duct tape. OK?
Or as my brother would say "that's just ducky."