T9 was single tap per letter and an internal dictionary would figure out which letter you meant, then 0 would cycle between possible matching words, with the last option falling back to the more common multi-tap input you're thinking of (which I don't recall ever having its own name) to add to the dictionary.
Yea, and Ken Kocienda would end up using a huge dictionary (bigger than any phone or the Newton which had one in 93 and a bigger one in 96) at the word level too.
But only after this prototype, because the design goal here was to validate that there was any way at all to type the letter you wanted. Design is not a linear thing, and that’s what I wanted to make people feel by recreating this early prototype!
Note that everyone in the team (15 developers) was busy creating their own weird keyboard too! Everything was halted because of the basic 1-to-1 keyboard failure to work
