Wikipedia (https://en.wikipedia.org/wiki/Hash_array_mapped_trie) links to the paper describing HAMT (https://infoscience.epfl.ch/server/api/core/bitstreams/f66a3...) and claims that is from 2000. That talk is from 2016.
HAMT weren't immutable/persistent until Clojure though: https://en.wikipedia.org/wiki/Persistent_data_structure#Pers...
Still well before the talk.
Do you know of any implementation, that is well annotated/commented, so that it is easy to understand?