A brain trust refers to a group of smart advisers. The term evokes the era of trusts in the United States, which were institutions that controlled production of certain products (such as oil or steel). A brain trust thus refers to a group of advisers who control the intellectual and creative aspects of an organization.
The New Deal Brains Trust
In U.S. history, the term "brains trust" was used to describe the group of advisers that President Franklin D. Roosevelt assembled during the 1932 presidential campaign to help him develop policies and legislation to address the Great Depression. As the term became popularized it was shortened to just "brain trust."
The group included Roosevelt intimates (such as his wife Elanor Roosevelt and law partner D. Basil O'Connor), political associates (such as Democratic National Committee Chairman James A. Farley and Roosevelt's legal counsel Samuel I. Rosenman), a cadre of Columbia University professors (Raymond Moley, Adolf Berle, and Rexford Tugwell), senators, and others.
They were consulted by Roosevelt on a regular basis since May 1932. By the time of Roosevelt's nomination, Moley was the central figure.
For a list, see brain trust/Catalogs