This was written by Robert and Richard Sherman, brothers who have written songs like "It's A Small World" and "Chitty Chitty Bang Bang." They got the title when one of the brothers learned the word at summer camp in the Adirondack Mountains - it was a word only kids knew the meaning of and adults did not.
The Sherman Brothers wrote this for the Disney movie Mary Poppins. Robert Sherman Jr. explains:
"Many people comment that this song is just a tongue twister and that there's nothing more to it. Actually, this song is integral to the plot of the Mary Poppins motion picture. When Mary, Bert and the children escape into the magic world of Bert's street pavement pastel drawing, the foursome shares a "supernatural" adventure. Mary Poppins then, with the greatest of subtlety, gives the children a special, undilutable keepsake, just before it rains and the magic world washes away. That keepsake is the word, "Supercalifragilisticexpialidocious." The rain washes all the magic away, but because their collective memories remain intact, the children are able to keep a piece of Mary Poppins' magic. The word's repetition throughout the rest of the movie is evidence that Mary Poppins' magic is real, and not just a product of the children's imaginations. At the end of the movie, when Mr. Banks has lost everything, he looks down at the tuppence which his son had given him. He then utters Mary Poppins' word, a word he had heard his children say. Doing this serves as Mr. Banks's own baptism into the magical nanny's alternative perspective. Mr. Banks, it turns out is the protagonist of the Mary Poppins story. It is that word which becomes the key to his growth."
A copyright infringement suit was filed by Barney Young and Gloria Parker, who had claimed writing a song in 1949 entitled "Supercalafajaistickespeealadojus" and showing it to Disney in 1951. Says Sherman:
"There was a suit. In a nutshell, it was laughed out of court. That is to say, it lost because, the claim was fraudulent. There was no 1949 "Supercal" derivative word or song; nor would the Sherman Brothers have had access to it, if there were. Walt Disney did not conceive of the song, the Sherman Brothers did anyway. It was included in their 1961 script treatment and originally entitled "The Pearly Song". There was no copyright claim made with the registrar of copyrights (at least not one which predated 1963 - there may not have even been one after that date, I can't speak to that.) There was no proof that the alleged 1949 song was even published or shown to Walt Disney! There is a lot of faulty information on this case, a lot of it made up, like the claim itself. Of course when reading a court summary forty years later, it can look like there might have been something there and that Disney just had bigger guns and squashed the little guy. Common sense will win out though - I think - in the end. After all, why would somebody have written a spec-song in 1949 called, "Supercalafajaistickespeealadojus" in the first place? If there had been, there would have been a very strong case against the Sherman Brothers and Disney - and Walt Disney would have most likely held some resentment toward the Sherman Brothers. But there was not and he did not. In the end it was a just a nuisance claim. The claim as well as the subsequent 'folklore' which has accompanied it through the years seems to defy any reasonable logic. It would be nice if it would go to bed!"
An urban myth has had sprouted that the word was connected to Irish or Scottish prostitution.
On the television program 100 Greatest Songs From Musicals, Julie Andrews said of this song, "It was such a catchy tune, it had such a rumpty tumpty flavour, a vaudeville flavour, I immediately identified with that as my background as a child was vaudeville." (thanks, Edward Pearce - Ashford, Kent, England)
An outrageous pun on the title of this song appeared in the Sun newspaper in February 2000. A major soccer match in Scotland pitted underdogs Inverness Caledonian Thistle against Celtic, one of the top teams in the country. After Thistle thrashed the favorites by three goals to one, someone at the paper came up with the magnificent headline "SUPER CALEY GO BALLISTIC CELTIC ARE ATROCIOUS." (thanks, Alexander Baron - London, England)