To shout in a deep, loud voice, or the deep loud noise itself; also a tool that blows air (like for a fire).
From Old English 'bielgan' meaning to swell or blow. Related to 'belly' (the swollen part). The tool meaning comes from the device used to blow air into fires since medieval times.
The word 'bellow' captures something physics professors love: the bellows in medieval blacksmith shops were the ancestors of all air pumps and air compressors we use today—from car tires to HVAC systems.
Complete word intelligence in one call. Free tier — 50 lookups/day.