Retronym is the word for a term created to rename an older thing after a newer version appears. Before the new version existed, the old thing usually needed no special label.
For example, people once just said watch. After digital watches became common, analog watch helped distinguish the older style. The same pattern gave us snail mail after email became common.
Retronyms often appear when technology changes, but they are not limited to technology. They help speakers be more precise when one original category splits into two or more familiar types.
- analog watch, contrasted with digital watch
- snail mail, contrasted with email
- landline phone, contrasted with mobile phone
- acoustic guitar, contrasted with electric guitar
- silent film, contrasted with talkies or sound films
So the next time you hear a phrase that sounds like an older thing being newly labeled, you may be looking at a retronym.