'regularly-seen' originates from the combination of 'regularly' and 'seen', where 'regularly' means 'at regular intervals' and 'seen' is the past participle of 'see', meaning 'to perceive with the eyes'.

'Regularly' comes from the Latin word 'regularis', and 'seen' is derived from the Old English 'seon'.

Initially, 'regularly' meant 'in a straight line', and 'seen' meant 'perceived'. Over time, 'regularly-seen' evolved to mean 'frequently observed'.