What is pseudo?

Answer 1

https://en.m.wikipedia.org/wiki/Pseudo-

Answer 2

Pseudonym = Alternative name ( fake )

Pseudo is either a contraction of pseudonym or
a prefix meaning roughly : supposedly.
pseudoscience, pseudonews, ... it is used in a derogatory manner to express contempt for something.

Pseudonym is also made of that prefix + nym
meaning roughly supposed ( assumed ) name.
No negative undertone here.