Satoshi Nakamoto always referred to it as such:
block chain
However, I see the term "blockchain" used a lot anyways. Do you think we should use Satoshi's terminology to prevent confusion with Blockchain.info, who will usually just refer to themselves as Blockchain? Or am I worried about nothing?

Somewhere along the lines it seemed like it belonged in a new word category
While a Block Chain is the same as a blockchain
People recognize it better together than seperately rather that is because it has become a force of habit or a force of adaptation I guess the former dominates
Block-Chain meets it half way just to throw that wrench in there XD (-) good old - sign