Retronyms are terms that became neccessary to distinguish the original from new alternatives. Some examples:
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George H.W. Bush
A rare example of a living person with a retronym. Until his son, George W. Bush, also became President, George Bush rarely, if ever, used his middle initials.
Manual transmission (Also standard transmission)
Automotive transmissions were all manual, of course, before the invention of the automatic transmission.
Star Wars Episode IV: A New Hope
Originally released in 1977 under the title Star Wars. The new title was applied in a 1981 re-release after the decision to make additional films, allowing Star Wars to refer to the entire series.
World War I
Originally this was called "The Great War" and commonly believed to be "the war to end all wars". However, when a second war enveloped Europe, Asia, and much of the Pacific, it became necessary to distinguish them. Similarly, the 1991 war in the Persian Gulf, formerly called "Desert Storm" or just the "Gulf War", is now (since the 2003 invasion of Iraq) often referred to as "The First Gulf War".
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as opposed to the kind that never makes any sound....
In the early days of the 1939 - 45 war, it was known as the Second Great War.
I have a series of vintage publications which refer to it as this.
Originally released in 1977 under the title Star Wars. The new title was applied in a 1981 re-release after the decision to make additional films, allowing Star Wars to refer to the entire series."
While this sounds like a good explaination for the name change it is untrue. George Lucas orginally wanted A New Hope to be titled episode 4, but Fox decided that it would be to confusing for audiences.