Retronym
A retronym is a newer name for an existing thing that helps differentiate the original form from a more recent one. It is thus a word or phrase created to avoid confusion between older and newer types, whereas previously (before there were more than one type) no clarification was required.
Advances in technology are often responsible for the coinage of retronyms. For example, the term acoustic guitar was coined with the advent of electric guitars; analog watches were renamed to distinguish them from digital watches once the latter were invented; "push bike" was created to distinguish from motorbike and motorized bicycles; and finally "feature phone" was also coined behind smartphones.
Etymology
The term retronym, a neologism composed of the combining forms retro- (from Latin retro, "before") + -nym (from Greek ónoma, "name"), was coined by Frank Mankiewicz in 1980 and popularized by William Safire in The New York Times Magazine.
In 2000 The American Heritage Dictionary (4th edition) became the first major dictionary to include the word retronym.
Examples
The global war of the early 20th Century from 1914 to 1918 was referred to at the time as the "Great War". However, after World War II (also known as the Second World War) erupted in 1939, the Great War was gradually more commonly referred to instead as World War I or the First World War.
The first bicycles with two wheels of equal size were called "safety bicycles" because they were easier to handle than the then-dominant style that had one large wheel and one small wheel, which then became known as an "ordinary" bicycle. Since the end of the 19th century, most bicycles have been expected to have two equal sized wheels, and the other type has been renamed "penny-farthing" or "high-wheeler" bicycle.
The Atari Video Computer System platform was rebranded the "Atari 2600" (after its product code, CX-2600) in 1982 following the launch of its successor, the Atari 5200, and all hardware and software related to the platform were released under this new branding from that point on. Prior to that time, Atari often used the initialism "VCS" in official literature and other media, but colloqually the Video Computer System was often simply called "the Atari"
The first film in the Star Wars franchise, Star Wars, was released in 1977, but was renamed Star Wars Episode IV: A New Hope in 1981, one year after the sequel The Empire Strikes Back was released.
In the 1990s when the Internet became widely popular and more people began to register for email accounts, the postal service was commonly referred to as "snail mail", and email was referred to as "mail" at times.