Green’s Dictionary of Slang

suet-headed adj.

foolish, stupid.

1876		Huddersfield Chron. 8 Jan. 3/2: To Sir William Harcourt on the festive occasion which he enjoyed [...] of cutting up and serving out with his own sauce the ‘suet-pudding-headed’ Government.
1915		Eve. Sun (Baltimore, MD) 9 Feb. 4/5: The suet-headed sage would find difficulty in convincing the millions of decent fellows.
1890		Bird o’ Freedom 22 Jan. 7: So we are bounced out of Croydon? Thanks to a batch of suet-headed crack-pots, this year will see the last of the merry Woodside meetings.
1948		Dly News (NY) 20 Oct. 11/1: Please resist that impulse [...] until after you’ve consulted a few levelheaded friends outside your notoriously suet-headed palace guard.
1951		Dly News (NY) 29 June 35/1: Truman [...] dragged the United States into this suet-headed Korean adventure.
1966		Times (Munster, IN) 1 Mar. 10/5: An ad that promised to teach them enough conversational French to dazzle their suet-headed escorts.