Grammar: duct tape or duck tape?
It is spelt correctly as duct tape, not 'duck tape'.
For those who care to know, the story goes like this: the Dutch word doeck for linnen cloth entered the English language in the 1640s as duck. This cotton and linnen fabric was used for sails and clothes. By 1899, one company in New Orleans developed an adhesive tape made from waterproof duck fabric. The cables on the Brooklyn bridge were protected by 100,000 yards of the stuff by the turn of the century.
That said, however, the first recorded use of duct tape according to the OED is an example from Wisconsin dated 1965. (Gaffer tape first appeared in 1977.) It is this spelling that has now become the standard English spelling around the world. Why? One reason is that 'Duck tape' is a trademark of the Duck Brand company and this needs a capital D. Use of the archaic and generic 'duck tape' that is not associated with said brand, with a small d, is technically trademark matter. Stick to the standard form, 'duct tape'.
About the author
Jesse Karjalainen is the author of The Joy of English: 100 conversations about the English Language, Cannibal – the language and history of the discovery of the New World, and Roanoke – the language and history of Early Colonial America.