I did a bit of searching on Google Books and there is an article from the June 28, 1972
issue of ComputerWorld that states "Ever since Hitachi introduce the Hitac 10 as a
'personal computer' in 1969, not only the regular computer manufacturers but
electric appliance, calculator, watchmakers, communications and software companies, and
even textile manufacturers, have plunged into the minigame." While they are talking
about minis, what this does show is that the term "personal computer" was used
prior to the advent of the Altair.