Meaning of MIRROR in English
Yep, you guessed it. A mirror is something that you can see your reflection in. Most mirrors are made up of a sheet of glass a a sheet of metal. When light hits the metal, it reflects off it and produces an image that can be seen clearly on the sheet of glass. However, in the computer world, a mirror is an FTP server that has the same files on it as another server. It's purpose is to provide an alternate way to access files when the main FTP site is so swamped with people downloading files that other people can't get through. However, unlike real-life mirrors, when you download a picture off a mirror server, the image isn't backwards.
English glossary of computer and Internet terms. Английский глоссарий компьютерных и Интернет терминов. 2012