'capitulum' originates from Latin, specifically the word 'capitulum', where the root 'caput' meant 'head' and the diminutive suffix '-ulum' meant 'small'.

'capitulum' passed into Medieval Latin with specialized senses (e.g. a little head or chapter heading) and was later borrowed into English in technical and scholarly contexts as 'capitulum'.

Initially it meant 'little head' (a small head or head-like projection); over time the term came to be used for chapter headings, botanical flower heads, specific anatomical rounded surfaces, and certain zoological structures.