See study by R. G. Tugwell (1968).
The term "brains trust" (originally plural, the s was later dropped) was first coined in 1901 and used in a sarcastic sense in reference to the first American general staff of the U.S. President. In 1932, New York Times writer James M. Kiernan revived the term when he applied it to the close group of experts that surrounded United States presidential candidate Franklin Roosevelt. The term has since been applied in general sense to any close group of advisors.
Having an academic team was first suggested to Roosevelt in March 1932 by Roosevelt's legal counsel Samuel Rosenman. This concept was, perhaps, based on The Inquiry, a group of academic advisors President Woodrow Wilson formed in 1917 to prepare for the peace negotiations following World War I. The core of the first Roosevelt brain trust consisted of a group of Columbia law professors (Moley, Tugwell, and Burle). These men played a key role in shaping the policies of the First New Deal (1933). Although they never met together as a group, they each had Roosevelt's ear. Many newspaper editorials and editorial cartoons ridiculed them as impractical idealists.
The core of the second Roosevelt brain trust sprang from men associated with the Harvard law school (Cohen, Corcoran, and Frankfurter). These men played a key role in shaping the policies of the Second New Deal (1935-1936).