'equally-structured' originates from the combination of 'equal' and 'structure', where 'equal' meant 'the same in quantity, size, degree, or value' and 'structure' referred to 'the arrangement of and relations between the parts or elements of something complex'.

'equally-structured' evolved from the combination of the words 'equal' and 'structure' in modern English.

Initially, it meant 'having the same structure', and this meaning has largely remained the same in modern usage.