Leisure Suit Larry waaay back in 1987.
Here's a quote from Al Lowe himself, who's doing an AMA over at Reddit right now:
"It was the first game we beta tested at Sierra. I wrote a module that
recorded what you were doing when you asked a question the game didn't
understand. The beta testers collected the text file created and mailed
them to me on a floppy disk by horse back. I then sorted them and made
sure the game had some sort of answer for everything they asked. So the
games owes its intelligence to the beta testers."
I highly recommend the rest of the AMA if you're interested in old-school adventure games. It makes for a great read!