'dealkylate' originates as a modern chemical formation combining the prefix 'de-' (from Latin, meaning 'remove' or 'from') and 'alkylate' (itself from the root 'alkyl' plus the verb-forming suffix '-ate'). 'Alkyl' is a 19th-century chemical coinage naming a hydrocarbon radical.

'Alkyl' was coined in 19th-century organic chemistry to name certain hydrocarbon radicals; from that came the verb 'alkylate' (to introduce an alkyl group), and later the verb 'dealkylate' was formed by prefixing 'de-' to indicate removal.

Initially formed to denote the removal of an alkyl group, the word has retained that technical chemical meaning in modern usage.