What is "retronym"

n. A new word or phrase coined for an old object or concept whose original name has become used for something else or is no longer unique (such as ''acoustic guitar'' where ''guitar'' used to mean this but can now also refer to an electric guitar).

A retronym is a new name for something that differentiates the original from a more recent form or version.

Advances in technology are often responsible for retronym coinage. For example, the term " acoustic guitar" was coined at the advent of electric guitars and analog watches were thus named to distinguish them from digital watches.