Google gets it wrong. According to their 20 Year Usenet Timeline, the first post mentioning Macintosh and Lisa was made on August, 1982.
In fact, the earliest post mentioning Macintosh and Lisa was made several months earlier, in November of 1981. Note the contrived spelling "Mackentosh" which is probably how Google missed it.
Here it is:
In fact, the earliest post mentioning Macintosh and Lisa was made several months earlier, in November of 1981. Note the contrived spelling "Mackentosh" which is probably how Google missed it.
Here it is: