'autodecomposition' originates from Greek and Latin; specifically the Greek word 'autós', where 'aut-' meant 'self', and the Latin word 'decomponere', where 'de-' meant 'apart' and 'componere' meant 'to put together'.

'decomponere' changed into Old French 'decomposer' and Middle English 'decompose' (giving 'decomposition'), while the prefix 'auto-' from Greek 'autós' was later combined in modern English to form the compound 'autodecomposition'.

Initially, related elements meant 'to put apart' or 'to separate into parts'; over time the compound came to denote specifically a 'breaking down' process, and in modern usage 'autodecomposition' denotes breakdown initiated by the thing itself ('self-caused breakdown').