'infrequently-seen' originates from the combination of 'infrequent' and 'seen', where 'infrequent' means 'not occurring often' and 'seen' is the past participle of 'see'.

'infrequent' changed from the Latin word 'infrequens', and 'seen' is derived from the Old English 'seon', eventually forming the modern English term 'infrequently-seen'.

Initially, 'infrequent' meant 'not crowded or not often', and 'seen' meant 'perceived by the eye', evolving into the current meaning of 'rarely observed'.