All of which were similarly fractional implementations of Xanadu.

Ted Nelson coined the term hypertext in the 60s.

Turbo Pascal help was using hypertext. Many people were exposed to it by the 80s

Again, all of this comes from Ted Nelson. He also had philosophical antecedents, but in terms of software it was his dream of Xanadu that was the first hypertext system.

However, it’s worth pointing out that every attempt at Xanadu (under the name Xanadu) thus far has also turned out to be a fractional implementation of Nelson’s dream.