"Where does creamed corn figure into the workings of the universe? What really is creamed corn? Is it a symbol for something else?"
Garmonbozia was a substance that resembled, or indeed was, creamed corn. The term "garmonbozia" was synonymous with "pain and sorrow." It was a source of sustenance for certain spirits, including the arm.
After killing Laura Palmer, BOB and Leland appeared in the red room before Gerard and the arm, both of whom demanded, in unison: "Bob, I want all my garmonbozia." In response, BOB held his hand to Leland's stomach wound, causing it to disappear, and then threw a great amount of blood onto the floor. Moments later, the arm ate a spoonful of creamed corn.
Behind the scenes
In the original shooting script of Twin Peaks: Fire Walk with Me, the term "garmonbozia" appears in the final scene featuring BOB and the arm inside the red room; and also in the scene where the arm first appears in the movie while seated in front of BOB. The phrase in the script is simply "garmonbozia (corn)" – the clarification that the word refers to "pain and sorrow" appears only in the finished film, and then only in the on-screen subtitles.
The name may be inspired by ambrosia, the food that was said to sustain the ancient Greek gods' immortality.