It was supposed to be used to seal connection points in ductwork, hence the name. There are many companies that try to be cute and play on the common mispronounciation of "duck" tape.
The funny thing is, with all the stuff it is so useful for, the one thing it really sucks at is for use on ducting. Heat dries out the glue and accelerates the rotting of the fibers so it falls apart really fast when used on ducting.
I have a roll of the ultimate duct tape. 12 inches wide (a redneck wet dream) with a release layer of paper on the sticky side so you can cut it to fit then expose the glue after it is ready. I've had it for a year and never opened it but, when I saw it, I just had to have a roll.