In some English versions of Final Fantasy elemental spells are named Fire, Fire2, Fire3 while in others they're named Fire, Fira, Firaga (or Thunder, Thundra, Thundaga). At first I thought it was due to bad English translation, but the English translation is flawless. What does "Firaga" stands for?
Based on information in this link, the -a, -ga, -ja, etc. endings for spells appear to be a naming convention Square decided on that is rooted in a Japanese grammar structure similar to the english -er, -est (e.g. something described as greater is not as good as something described as greatest).
The suffixes (Fire, Fira, Firaga) have been used in Japan since the very beginning. Several other Japanese RPG series have done similar things, like Phantasy Star (Foi, Gifoi, and Nafoi) or the Persona series (Agi, Agilao, and Agidyne). They all refer to levels of a fire-based attack spell, but they follow their own pseudo-grammatical structures.
The early English translations of these games didn't allow enough space in spell names to translate straight across. FF1 only allowed four characters, and FF4 (which we called FF2 at the time) only allowed 5: neither one is enough. FF6 allowed for 6 characters, which would have been enough for Fire and Cure but not Blizzard or Thunder, so they kept the English convention to keep things consistent. When they started being able to use more free-form spell names, they used the Japanese convention everywhere.