'rarely-seen' originates from the combination of 'rarely,' meaning 'not often,' and 'seen,' the past participle of 'see,' meaning 'to perceive with the eyes.'

'rarely' evolved from the Old English word 'hrēor,' meaning 'seldom,' and 'seen' from the Old English 'gesēon,' meaning 'to see.'

Initially, 'rarely-seen' meant 'not often visible,' and this meaning has largely remained the same in modern usage.