Codex

Codex comes from the Latin word for "book." If you want a book to sound really fancy, render its title in faux-Latin and stick the word "Codex" in front, like "Codex: Canus Latinicus."

In Warhammer 40,000

Since Second Edition, each army book and expansion published by Games Workshop has been titled "Codex: Herpaderp." The term "Codex creep" refers to the fact that these Codices have been published across three editions and ten years, and it seems that the latest Codices (especially the half-dozen flavors of Space Marines) are more powerful than the older ones in order to entice people to buy the army of the month.

The word Codex is also used in the universe of Warhammer 40,000, like the Codex Astartes.