'demulcent' originates from Latin, specifically the verb 'demulcēre' (present participle 'demulcens'), where the prefix 'de-' and the root 'mulcere' meant 'to stroke' or 'to soothe'.

'demulcent' came into English from Late Latin/Medieval Latin 'demulcens' (present participle of 'demulcēre'), ultimately from Latin 'mulcere'; it entered English usage in learned/medical contexts and became the English adjective and noun 'demulcent'.

Initially it conveyed the idea 'that which soothes (by stroking or softening)'; over time it narrowed to mean specifically 'a substance that soothes or protects irritated tissues' in medical and pharmacological usage.