This author’s work on RITA appears to be the origin of the terms ‘user agent’ and ‘software agent’ & their use to describe small interacting autonomous software processes on networked machines.

I found it while trying to see if this use predates the use in email (and later HTTP), wherein the ‘user agent’ is the browser or email client.

RITA appears to be the origin of both senses, & they seem to have diverged quickly.