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Bovines have four stomachs through which their food undergoes different stages of digestion.

From the first, the rumen, comes the "blanket" tripe, so named because of its "pile". It varies in thickness and is often accompanied with a layer of fat which needs to be removed. The second stomach, the reticulum, produces "honeycomb" tripe, generally preferred by cooks because it keeps its shape during cooking and also because it holds, on its textured surface, the sauce in which it is cooked. Tripe from the third stomach, the omasum, is known as "bible", "book" or "seam" tripe.

http://www.tripesite.com/lore.html

По-русски этот отдел желудка жвачных называется "книжка", однако это название зоологическо-анатомическое; уточните по специализированным ресурсам, как это принято называть в мясообработке.