I think these questions are on-topic.
Many results are known to experts in a discipline, while the same experts may not be aware of who they are due to or of the specific publication where they first appeared. Knowing these details is actually rather useful beyond fulfilling a reference request. (Personally, I've seen this happen quite frequently, and while working on long texts, often I have longed for a community that may help me locate some of the early, and not so easily available references I have needed to identify.)
For instance, the countable chain condition (a property of partial orders) is used in set theory, where many experts agree that it should instead be called the countable antichain condition. The puzzling name actually makes sense once one sees the algebraic context where it originated.
For another example, there is a famous result of Sierpiński, usually stated as follows: Under the assumption of the continuum hypothesis, no well-ordering of the reals in order type $\omega_1$ is Lebesgue measurable (as a subset of the plane). The result is significantly more general: No additional set theoretic assumptions are needed, and it suffices to assume that the well-ordering is of a non-null subset of the line, does not have to be a well-ordering of optimal length, and the subset does not need to be assumed measurable. These remarks are not typically present in the measure theory books that cover the result, and most likely this is because the authors have not seen the original paper, but rather just the modern presentations that only cover the particular case. In his paper, Sierpiński starts with this case, but then explains how to generalize to the right version.
My point is: Original sources are very hard to locate, and being an expert in the technical aspects of a discipline does not imply that you can trace accurately the history of your subject to its original sources. Knowing these sources tends to add perspective. And these sources are more likely to be located by members of this community than by members of discipline-specific SEs, unless those members happen to have an interest in the history of their subject, in which case we actually want them here as well.