'actinoid' originates from the Greek word 'aktinos,' meaning 'ray,' combined with the suffix '-oid,' meaning 'resembling or like.'

'actinoid' was derived from the Greek word 'aktinos' and the suffix '-oid,' and eventually became the modern English word 'actinoid.'

Initially, it referred to elements resembling actinium, but over time it evolved to include a series of elements in the periodic table.