1. A name that the Sethians possibly self-identified by (Brakke, The Gnostics)
2. An archaic term for "perfected Christian" or "saint", evidence for this can be found in the writings of Clement of Alexandria.
3. A term mockingly used by St. Ireaneus to slam Christians he didn't like, namely the Marcionites, Sethians, and Valentinians. Here it started to become interchangeable with term Heretic.
4. Used by Marcellina, Carpocrates, to describe herself. It was either used in the context of "I am a perfected Christian" or "I'm a heretic, so?"
Gnosticism?
(Hanegraaff, New Age Religion and Western Culture, 152)
The term Gnosticism was originally a pejorative term, coined in the 17th century by the Cambridge Platonist Henry More. In adopting it as a purportedly neutral scholarly category, historians also largely took over the assumption that there had actually existed a distinct religious system which could be called Gnosticism, and which could be clearly defined in opposition to the early Christian church. In recent decades it has become increasingly clear, however, that any such reification of “Gnosticism” is untenable and leads to historical simplications; the idea of a clear-cut opposition of Christianity versus Gnosticism in fact reflects heresiological strategies by means of which certain factions and their spokesmen sought (successfully, as it turned out) to cement their own identity as “true” Christians by construing a negative other: the adherents of “the Gnosis falsely so called”, demonized as the enemies of the true faith.