Gandhara (not "Ghandara") is mentioned in the Behistun inscription of the Persian emperor Darius, from about two hundred years before Alexander, so it's clearly not "a corruption of Alexandria".
Oh really? Maybe that's wrong then. Is the name a transcription or a translation? What script were the records written in originally? Names can be retroactively applied, especially in translation. Looks like I've got some reading to do. Edit: Maybe I got confused between different folk etymologies for the name of the city of Kandahar.
Kandahar is a city; Gandhara was a kingdom. (But, yes, there is a theory that the name ["Kandahar"](https://en.wikipedia.org/wiki/Kandahar) derives from Gandhara, as opposed to deriving from "Alexander" -- though it seems generally agreed that there was a city -- [Alexandria of Arachosia](https://en.wikipedia.org/wiki/Alexandria_Arachosia) named after him built on that spot.)
That's what I thought as well, but clearly there's more debate there to be had than I realised. Was the city not founded by one of Alexander's generals or was it? Or ever called something like Iskanderha? I don't know.