I looked up the etymology of “uncanny” and it seems that it does mean the opposite of “canny”. But I don’t hear anyone using “canny”. I’ve never heard anyone use that word. But uncanny is used from time to time.

It's just an odd exception in English. I'm learning Spanish and there are often exceptions that you just have to accept. Don't get too hung up on the word 'uncanny' - while it does come up, it won't come up too often :).

I remember CANNY is used in the hobbit. Bilbo is supposed to scout out the trolls to see "if all is perfectly safe and canny."