"Some anonymous copy editor gave it a name, spun off from the Batman comic character who was then the subject of a popular TV series. He tagged the creature Mothman."
- John Keel, The Mothman Prophecies 1975, Page 78 Chapter 6
"Mothman" is the name given to a legendary winged monster of West Virginia by the local news press in November of 1966. The name is based off of the comic book character Batman which had a popular television series at the time starring Adam West. The name is a bit of a misnomer because the creature was actually reported to be a bird-like man with wings and red eyes. He was not reported to be a Moth or in any way Moth-like. Locals of Point Pleasant WV simply referred to him as "The Bird".
A November 17th 1966 headline from the Herald-Dispatch in Huntington seems to be one of the earliest examples of the name. It read: "Bird, Plane or Batman? Mason Countians Hunt 'Moth Man'". The next day on November 18th 1966, the Huntington Advertiser printed the headline "Could the 'Moth Man' Be Balloon?" Later on November 19th 1966 a headline from the Herald-Dispatch read: "That Mothman: Would You Believe A Sandhill Crane?".
The name appears to have started off as "Moth Man" then combined into the singular word "Mothman". Other Newspapers at the time referred to him by terms such as "Man-Sized Bird", "Thing", "Creature" or "Monster". They also called him a "Bird-Like Creature", "Winged Monster", "Bird Monster", "Bird" or "The Bird". As the name Mothman was repeated, some of the other papers eventually followed along and used the name as well.
In the year 1970, New York author John Keel released a book titled Strange Creatures From Time And Space which contained a chapter about the creature titled "West Virginia's 'Mothman'".
Later in 1975, John Keel released a book titled The Mothman Prophecies which documented his account of the legend. This title was however not of his choosing, it was the publisher which changed it last minute. The book was originally set to be titled The Year of The Garuda in reference to the bird-like being from Hindu and Buddhist Mythology.
The book's title containing the word Mothman definitely contributed to the name's popularization. It was then further popularized when the 2002 film adaption was released. The public interest in the legend sparked by the film led to the creation of the Mothman Festival in the town of Point Pleasant, the Mothman Statue by Bob Roach and the Mothman Museum founded by Jeff Wamsley.
Books and documentaries released after the name's popularization continue to use the name Mothman as a recognizable label for the legendary creature. The name has been firmly cemented as a term to refer to this red-eyed winged monster of West Virginia folklore.
Sources: Strange Creatures From Time And Space by John Keel (1970) (Chapter 18) The Mothman Prophecies by John Keel (1975) (Quote page 78 and 1991 Print Afterword) https://en.wikipedia.org/wiki/Garuda http://www.wvculture.org/history/notewv/mothman.html (Newspaper Date/Publication Archive) Mothman: The Facts Behind The Legend by Jeff Wamsley and Donnie Sergent Jr. (2001) (Newspaper Archive) Mothman... Behind The Red Eyes by Jeff Wamsley (2005) (Newspaper Archive) Mothmanfestival.com Mothmanmuseum.com
Strange Connection: Mothman = Batman = The Shadow
The 1930's pulp novel character The Shadow is mentioned in Chapter 1 of John Keel's The Mothman Prophecies. This is interesting because The Shadow heavily inspired the creation of the character Batman and Batman of course inspired the newspapers to coin the name Mothman.
To bring it full circle, the author who wrote most of The Shadow novels and was credited with the creation of the character was a man named Walter B. Gibson who knew John Keel. They both lived in New York and had an interest in the art of illusion. They also shared a mutual respect for the work of Magician Harry Houdini. John Keel seemed to be a fan of The Shadow. The character of The Shadow was created as a radio advert but the books were inspired by Sherlock Holmes and Dracula.
Sources: The Mothman Prophecies by John Keel (1975) (Page 18, Chapter 1 III.) The Shadow http://www.johnkeel.com/?p=2390 https://en.wikipedia.org/wiki/The_Shadow The Living Shadow by Maxwell Grant (April 1st 1931) (Walter Gibson under pseudonym) https://en.wikipedia.org/wiki/Walter_B._Gibson The Shadow Scrapbook by Walter B. Gibson (1979) The Mothman Prophecies by John Keel (1975) (Page 78, Chapter 6 I.) Batman https://en.wikipedia.org/wiki/Batman#Creation