The term was coined for Fuller approximately in 1928 by Waldo Warren, an advertising expert who had previously become known by inventing the word "radio" for what people used to call "the wireless" at the time. A brand name was needed for the display of Fuller's first architectural model, later to be known as the Dymaxion house.
In order to come up with a word, Warren spent two days listening to Fuller and trying to get a feel for the type of language he used. He then played randomly with syllables from typical Fuller words, until the word "Dymaxion" was born.
Fuller was very excited about the word and used it for many of his inventions in the decades to follow, including the Dymaxion house, the Dymaxion car, and the Dymaxion World Map. He also renamed his elaborate journal, in which he sought to document his life as an experiment with the greatest possible detail, as the Dymaxion Chronofile.