'pneumoperitoneum' originates from Greek, specifically the words 'pneuma' meaning 'air' and 'peritoneum' referring to the membrane lining the abdominal cavity.

'pneuma' and 'peritoneum' combined in medical terminology to form the modern English word 'pneumoperitoneum'.

Initially, it referred to any air in the abdominal cavity, but over time it evolved to specifically denote air introduced for medical purposes.