retronym

[ re-truh-nim ]
/ ˈrɛ trə nɪm /

noun

a term coined in modification of an original term that was used alone (as acoustic guitar instead of guitar ) to distinguish it from a term referring to a later development (as electric guitar ). Other examples of retronyms are snail mail and analog watch.

Origin of retronym

1980, Americanism; retro- + (-o)nym; coined by Frank Mankiewicz, U.S. journalist