Translation:Which way is north?
どっち is the casual version of どちら
どっちら doesn't exist, as far as I know.
I believe that どちら comes from adding ～等【ら】、a humble/derogatory suffix for pluralization (which can also be used to indicate location or direction) to どち which is also where どっち comes from, and which I believe comes from a phonetically modified version of 土地【とち】"plot of land, place". This suffix is very similar to the ～ら in 彼ら、いくら、何ら、これら、お前ら for example.
The reason why どっち doesn't have a ～ら、It's probably because this ら is added in order to be humble before the listener (only when is not used with a personal pronoun to address people), and since どっち is supposed to be the casual version, well, you can put two and two together.