'rarely-believed' originates from the combination of 'rarely,' meaning 'not often,' and 'believed,' the past participle of 'believe,' which comes from Old English 'belȳfan,' meaning 'to hold dear, love, trust.'

'belȳfan' transformed into the Middle English word 'bileven,' and eventually became the modern English word 'believe.'

Initially, 'believe' meant 'to hold dear or love,' but over time it evolved into its current meaning of 'to accept as true.'