It is a fictional account of the time of the Russian purges in the 1930s, and it focuses on what happened to Osip Emilievich Mandelstam. Littell says: "The publication of his first book of poetry in 1913, entitled Stone, established him in the eyes of many as "the" great Russian poet of the twentieth century, a view that Stalin clearly shared." Of course, Mandelstam dies in a prison camp. He is on a train, taking him to Siberia. Also in the cattle car with Mandelstam is a professor who organizes their car and thus gets its passengers to the first major stop without any loss of life. Then on p. 265:For those not familiar with the history of this quip, you can start here.
"I overheard a lady mention what the professor was a professor of. It turned out to be something called linguistics. The lady said that he was famous for figuring out the difference between languages and dialects -- languages were spoken by people with armies, dialects by people without."
The image is of Mandelstam.