'O-deethylisation' originates from English, formed from the letter 'O' (indicating attachment to an oxygen atom), the prefix 'de-' meaning 'removal', the root 'ethyl' referring to the ethyl group, and the noun-forming suffix '-isation' (British spelling) used to indicate a process.

'O-deethylisation' is a modern chemical coinage that developed in 20th-century organic chemistry and pharmacology by combining established elements: 'deethylation' (or 'de-ethylation') and the process noun ending '-isation', resulting in the current term used in biochemical and metabolic contexts.

Initially the components meant 'removal' ('de-') of an 'ethyl' group attached to 'O' (oxygen), and over time the combined term has been used specifically to denote that particular metabolic/chemical process without change in the core idea.