I am an engineer by trade, and this phrase is often used in a somewhat derogatory way to indicate knowledge which is passed around in an organization, but never documented or standardized. A Wikipedia article indicates it is used in the Six Sigma community, which is probably the reason I've been exposed to the term, but I am curious to know if it is used elsewhere, where it came from, and if others use another word or phrase for the same idea.
Tribal Knowledge is a term that can be used everywhere, because a tribe is basically a group or subgroup of people, not necessarily a division of an race. This word can be used like in this situation.
It is only generally used around corporations, businesses, offices, etc.
Synonyms include:"institutional memory," or as Martin suggested in a comment above,"institutional knowledge"
But neither of them are as well-known as tribal knowledge.
As I was reading your question a great near-synonym jumped into my mind that I first encountered in A Confederacy of Dunces: “folkways”.
If that provides a different colour to what you're looking for, I would also suggest “lore” as having different overtones to the “folklore” that another contributor already provided.