Origins of the term "distributed hash table"
The term can at least be traced back to a publication by Carriero, Gelernter and Leichter from 1986: Distributed Datastructures in Linda[Lin86]. The paper attributes the term to Rob Bjornson (which I believe to be this guy), but only cites personal communication as their mean of learning the term. [Lin86] also refers D. Gelernter: Dynamic global name spaces on network computers. (1984), which is said to propose an implementation. I didn't find the paper, so I can not say if this is true. Another report (which I didn't find as well) by Leichter is said to discuss the implementation further: Implementing the Unimplementable -- Algorithms for Linda's Tuple Space.

The source in Linda seems to be a dead end, but was the oldest source of the term that I could find. I think it could be attributed with the term, but I may be confuted. If we assume that Bjornson came up with the term, at least the time frame would be fitting. Bjornson started his work in 1984, so if he is attributed with the term, the term's origin would neatly fit into the time were the Linda papers above were written.