​There was certainly a spell by v6 in 77 timeframe, I relied on it and remember adding words to it because the dictionary was small.  There was also very slick side program called 'grope' that I was told was developed using the spelling algorithms for the Bell Telephone 411 operators that one of the OYOC folks brought with them [Karn maybe - I've forgotten whom].   It had a different dictionary - that was its only disadvantage - so you had to have two dictionaries on the system [grope split the words into 26 files and the indexed them in a interesting fashion].   But being someone that can not spell to save myself, grope was a life wonderful addition to my tool kit.