A retronym is a term consisting of a noun and a modifier which specifies the original meaning of the noun. For example, organic food is a retronym: a long time ago, all food was what we now consider "organic." Retronyms can be objects (pedal bike), experiences (snow skiing), or even places (meatspace). Most of us use retronyms all the time without thinking about it.
The oldest print usage that we know of for the word retronym itself is from William Safire's column "On Language" in a 1980 issue of The New York Times. There, he discusses how then-president of National Public Radio, Frank Mankiewicz, collects what he calls "retronyms."