Retronyms:

Ian Lumsden (speling approximate) wrote to the Daily GizWiz podcast (#508) to explain the rather appealing concept of "retronyms". A retronym is necessarily (but not inclusively) a qualified noun that has had to replace a generalized noun to refer accurately to some older technolgy. Before your eyes glaze over, examples are: acoustic guitar, analog clock, hard disk, and dial phone.

Before the electric guitar, we just called those objects "guitars", but now we must distinguish. Once, all disk drives were "hard", but we did not acknowledge that until there were floppies. And so on.

Perhaps you've come across this old puzzle: someone digs up a coin with the numeral five on it, a picture of a regal figure, and the inscription: In the reign of King Henry the First. Is it a fake? Of course! During his reign he was just King Henry, not "the first." Retronyms.