The song Supercalafajalistickespialadojus (the super song) was published and recorded in 1950,
When Disney were sued for ripping off the song in 1964 they claimed it was a common slang word but here the Sherman brothers writers of Supercalifragilisticexpialidocious describe how they 'invented' the word.
So either it was a common slang word, a word that two sets of song writers invented, a word that one set invented and the others 'borrowed' or it was put in their minds by a supernatural force.
Nice tunes both of them.