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.)