Retronym is a noun that refers to a term to distinguish the original older version of something.

Our word of the day’s prefix R-E-T-R-O refers to a revival of something, by adding the suffix N-Y-M, meaning ‘name,’ we get a word that means ‘a name for something old.’ More specifically, a word for something old that has been replaced by something newer. For example: It still seems odd to me to refer to my phone as a ‘land line.’ I tend to forget that for younger people, most of their phones are cell phones. That’s why it is necessary to use the retronym ‘land line.’