The Origin of Supercalifragilisticexpialidocious

There's a very nice (slightly dated) interview from LAist of songwriter Richard M. Sherman in which he explains how the Mary Poppins song was created. A wonderful brain exercise;

How did you make up the word Supercalifragilisticexpialidocious ?

That's a word we sort of concocted from our childhood when we used to make up double talk words. In the screenplay version of Mary Poppins we wanted Her to give the children a gift they could bring back with them from inside the chalk drawing when they came out into the real world. If it was a tangible thing like a seashell or pine cone it would disappear. So we said, Remember when we used to make up the big double talk words, we could make a big obnoxious word up for the kids and thats where it started. Obnoxious is an ugly word so we said atrocious word, thats very British. We started with atrocious and then you can sound smart and be precocious, we had precocious and atrocious and we wanted something super colossal and thats corny, so we took super and did double talk to get califragilistic which means nothing, it just came out that way. That's in a nut shell what we did over two weeks. All together you get Supercalifragilisticexpialidocious.