FIT is derived from the English word "fit". FIT also comes with a wish of "the car that fits every scene of everybody's life". The sales catalog and TV commercial were completed on the premise that this car will be released under the name "Fitta". However, Fitta was found to mean a female genital in France and Sweden, so this car's name was suddenly changed to "Fit" from "Fitta" before release.
ARIA is derived from "a solo song sung in an opera". ARIA also comes with a wish of "the car that release everyone's hearts like music and brings the joy of driving like a sing freely".