Definition of the word zip up

The phrase "zip up" as we use it today to mean fastening a zipper refers to the sound the zipper teeth make as they come together. Zippers as we know them were actually patented in 1913 by Gideon Sundbäck, a Swedish immigrant living in the United States. The name "zipper" is said to have been coined by B.F. Goodrich, who began using the fasteners on his rubber boots in the 1920s. Initially, the sound of the zipper teeth coming together was called a "crocodile snap." This was inspired by the resemblance the closed zipper teeth bore to the jaws of a crocodile. However, "crocodile snap" wasn't a practical term for the sound since it didn't accurately describe the action of pulling the zipper up to fasten it. Eventually, in the 1930s, people began to say "zip it up" as a slang term for actually closing the zipper. This phrase later evolved into "zip up" as we use it today, the action of pulling the zipper up having replaced the symbolism of closing the "crocodile snap." So the next time you hear someone say "zip up," you'll know that they're not suggesting you should remain silent, but simply reminding you to fasten your jacket or pants before heading out into the world!