'deethylate' is formed from the prefix 'de-' (from Latin 'de-' meaning 'away, off, remove'), combined with 'ethyl' (the chemical radical name) and the verb-forming suffix '-ate' (from Latin/Old French usage to form verbs).

'Ethyl' was coined in modern chemical nomenclature in the 19th century (derived ultimately from Greek aither/ether via Latin/French forms) to name the –CH2CH3 radical; combining it with the prefix 'de-' and suffix '-ate' produced the modern chemical verb 'deethylate' in technical usage.

Initially built to denote the literal removal of an ethyl group in chemical contexts, the term has retained this specific meaning and is used in both organic chemistry and biochemistry (e.g., metabolic deethylation).