Interesting question, I looked it up earlier this summer and, unfortunately, the results aren't satisfactory but do shed some light on the topic. Have a look at the following links:
The words block and chain were used separately in Satoshi Nakamoto's original paper but were eventually popularized as a single word - blockchain, by 2016 -Wikipedia
Hope it helped you!
Wrong. Hal passed away 4 or 5 years ago (I don't remember exactly). Not sure where you got this since it isn't mentioned in the link you posted. (or I missed it) But it's definitely wrong as Hal wasn't alive in 2016