The Novice Keepers Lexicon is a semi-canon low-spoiler collection of names and concepts from Thief: The Dark Project (before Thief Gold). It is hosted by Thief-TheCircle.com, and has no affiliation with Looking Glass Studios beyond that. Some subjects in the Lexicon have been criticized , and should only be considered canon if it does not contradict Thief canon.
And, as always, if anybody knows the canon source for "Barak" or "Lord Janco", please share, because the original author of the Lexicon neglected to take note of his sources, which must now be assumed to have been lost to time. It is also possible these names were included in the Lexicon due to a misunderstanding of a non-canon source.