The time traveller is confused and disoriented and meets a man in a park.
He babbles about the future and says "parts of this may sound like science-fiction".
This is the only bit of the conversation the other man hears clearly and after the time traveller returns to the future he wanders off muttering about 'scienti-fiction'.
It transpires that this individual was responsible for naming the genre.
I read this in an anthology sometime in the 1970s.
Birth of a Notion, by Isaac Asimov
Simeon Weill, a physicist, experiments with time travel and travels back to New York City in 1925, where he meets Hugo Gernsback, a science fiction author and Weill's hero.
Although only given a few minutes sitting with Gernsback on a park bench, he manages to convey to the author some of the scientific developments to come in the next fifty years. Just before being transported back to 1976, he suggests that Gernsback's proposed science fiction magazine be titled Amazing Stories.
Hugo Gernsback was the person who coined the term "Scientifiction"
