'accidentally-built' originates from the combination of 'accidentally' and 'built', where 'accidentally' comes from Latin 'accidentalis', meaning 'happening by chance', and 'built' is the past participle of 'build', from Old English 'byldan'.

'accidentally' evolved from the Latin 'accidentalis' through Old French 'accidental', and 'built' from Old English 'byldan', eventually forming the modern English term 'accidentally-built'.

Initially, 'accidentally' meant 'by chance', and 'built' meant 'constructed'. Together, they describe something constructed by chance.