'commonly-seen' originates from the combination of 'common' and 'see', where 'common' meant 'frequent' and 'see' meant 'to observe'.

'Common' and 'see' were combined in modern English to form the adjective 'commonly-seen'.

Initially, 'common' meant 'frequent' and 'see' meant 'to observe', and this meaning has largely remained the same in modern usage.