From The Free On-line Dictionary of Computing (19 January 2023):
pseudo
<jargon> /soo'doh/ (Usenet) Pseudonym.
1. An electronic-mail or Usenet persona adopted by a human
for amusement value or as a means of avoiding negative
repercussions of one's net.behaviour; a "nom de Usenet",
often associated with forged postings designed to conceal
message origins. Perhaps the best-known and funniest hoax of
this type is BIFF.
2. Notionally, a flamage-generating AI program simulating
a Usenet user. Many flamers have been accused of actually
being such entities, despite the fact that no AI program of
the required sophistication yet exists. However, in 1989
there was a famous series of forged postings that used a
phrase-frequency-based travesty generator to simulate the
styles of several well-known flamers; it was based on large
samples of their back postings (compare Dissociated Press).
A significant number of people were fooled by the forgeries,
and the debate over their authenticity was settled only when
the perpetrator came forward to publicly admit the hoax.
(1995-03-13)