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.