Disney most likely took the name from the TRON command which is/was a debugging feature in BASIC [0]. The site itself also (whether conciously or not) make no mention of the movie. "Tron" could also be an shortening of "Electron" but without the hassle of an apostrophy, e.g. 'tron-club. I could be talking bollocks though :)
[0]: https://en.wikipedia.org/wiki/TRON_command