'mandatorily-built' originates from the combination of 'mandatory' and 'built', where 'mandatory' comes from Latin 'mandatorius', meaning 'obligatory', and 'built' is the past participle of 'build', from Old English 'byldan'.

'mandatorius' transformed into the English word 'mandatory', and 'byldan' evolved into 'build', eventually forming the modern term 'mandatorily-built'.

Initially, 'mandatory' meant 'obligatory', and 'built' meant 'constructed'. The combined term retains the essence of these meanings, emphasizing construction required by law.