Why does Final Fantasy contain "Final" in the title? Why does the Final Fantasy franchise of RPGs, anime, manga, etc. contain "Final" in the title?


Is it that the original concept of the first game was intended to portray the ending of a story? Was it derived from in-universe content?
Or is it because the creators did not plan to produce more games, and did not expect that any sequels would be desired?
Or was the inclusion of the word "final" chosen for a completely reason?
Hironobu Sakaguchi, a designer at Square (the company who developed Final Fantasy), was essentially creating what he saw as a magnum opus. After his lack of success with previous Square titles (nearly leading to its bankruptcy), this was his final attempt to live out his fantasy of developing games.
From Wikipedia:

Though often attributed to the company allegedly facing bankruptcy, Sakaguchi explained that the game was his personal last-ditch effort in the game industry and that its title, Final Fantasy, stemmed from his feelings at the time; had the game not sold well, he would have quit the business and gone back to university.

Wikipedia attributes this to another article, with a direct quote:

“The name ‘Final Fantasy’ was a display of my feeling that if this didn’t sell, I was going to quit the games industry and go back to university. I’d have had to repeat a year, so I wouldn’t have had any friends – it really was a ‘final’ situation.”
  — Hironobu Sakaguchi