coelom

mentioned: body cavity
https://doi.org/10.1351/goldbook.10543

Body cavity, found in many animals, lined with mesodermal epithelium and containing the digestive tract and other visceral organs

Note: The principal cavities of the trunk arise from the intraembryonic coelom.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 738 (https://doi.org/10.1515/pac-2015-1202)