'opioid' originates from the Greek word 'opion,' meaning 'poppy juice,' combined with the suffix '-oid,' meaning 'resembling or like.'

'opion' transformed into the Latin word 'opium,' and eventually became the modern English word 'opioid' through Middle English.

Initially, it referred to substances derived from opium, but now it includes both natural and synthetic substances that act on opioid receptors.