system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How does C3PO know the language of the Sith?

Who programmed that language into his memory banks and why would someone go thru the trouble of then prohibiting him from translating it?
gpt
It's unlikely each language was programmed individually, likely there is a galactic database of languages that all protocol droids with translation functions are created using.

At some point the sith language was added to that database, and then later the restrictions were placed on it, probably a long time ago by the republic around Darth Banes time when the sith ceased to be a galactic power.