The story
From pleuro- + peritoneum.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: The pleural and peritoneal membranes, or the membrane lining the body cavity and covering the surface of the enclosed viscera; the peritoneum; used especially in the case of those animals in which the body cavity is not divided Full definition →
From pleuro- + peritoneum.
Etymology from Wiktionary, CC BY-SA 4.0.