A recent entry on PVRBlog got me curious, and I needed a break from work, so I did some Googling.
This is the oldest post I can find from someone at TiVo. November 5, 1997
This is the oldest business related post I can find. July 8, 1998
This is the first external mention I could find. October 3, 1998
Oh, in case you didn’t know, TiVo was originally name Teleworld. They changed their name before shipping the first units.