The written name
Modern Japanese writes it 富士山, read Fujisan. The characters mean roughly abundance and gentleman or warrior, but they were chosen for sound rather than meaning, so they do not explain the origin.
Background
What Fuji means.
The name is older than its kanji and nobody can prove a single origin. Here are the theories that scholars actually take seriously, and how to say it the way people do in Japan.
Origins
Where the name comes from
Never ending, fushi
One old reading links Fuji to fushi, not dying or never ending, tied to the immortality legend in the Tale of the Bamboo Cutter where an elixir is burned on the summit.
Ainu origin
A popular theory connects the name to an Ainu word for fire or a fire deity. Linguists dispute it because Ainu settlement this far south is uncertain, but it keeps appearing in guidebooks.
Wisteria and slopes
Other proposals derive Fuji from fuji, wisteria, or from words describing a long even slope. The oldest surviving mentions in the Man'yoshu already use several spellings.
Why not Fujiyama
Yama and san are both readings of 山. Japanese speakers use Fujisan, and the san also reads as an honorific, which fits a mountain that has been worshipped for centuries. Fujiyama is a foreign coinage.
Konohanasakuya hime
The mountain's enshrined deity is Konohanasakuya hime, goddess of blossoms and of the volcano's calm. Her Sengen shrines ring the base and give Fuji its other name, Sengen.
Plan