'chlorinate' originates from Modern English formation based on 'chlorine', ultimately from Greek 'khlōros', where 'khlōros' meant 'greenish-yellow' and the verb-forming suffix '-ate' (from Latin/French) meant 'to make or treat with'.

'khlōros' (Greek) → 'chlorine' (coined in early 19th century English for the greenish-yellow gas) → 'chlorinate' formed in English by adding the suffix '-ate' to mean 'to treat with chlorine'; 'chlorinated' developed as the past/past-participle and adjectival form.

Initially associated with the greenish-yellow color implied by 'khlōros' and the gas 'chlorine'; over time it came to mean specifically 'to treat with chlorine' or 'to introduce chlorine into a compound', a meaning that remains today.