In this question Bruce James ponders "How can I know a Rav has Daas Torah". I am wondering what is the earliest source that gave this concept its name?
The clearest earliest source we have for the modern concept of Daas Torah can be found in "Chafetz Chaim Al Hatorah". Rav Shmuel Greineman quotes in the name of the Chafetz Chaim:
It describes a Rabbinic perception, derived entirely from Torah, non-secular sources, which is then able to provide a resolution to all worldly problems.
Source from Rabbi Anthony Manning.
Although, Rav Hillel Goldberg in "Between Berlin and Slobodka" and in Tradition (23:4 summer 1988) "Israel Salanter and Orhot Zadikkim Restructuring Mussar Literature" claims the source is even earlier and is attributed to Rav Yisroel Salanter the founder of the Mussar movement.
However, Lawrence Kaplan disputes this claim.
This is what is usually meant when people say Daas Torah.
The question you linked to is mislabeled IMHO. He discussing bans and prohibitions which are well within the jurisdiction of the Rabbinic community, but for some reason these Rabbis don't seem to be too good at it.
(Ty to Yishai DoubleAA and Hodofhod for corrections and links)