'accidentally-formed' originates from the combination of 'accidentally' and 'formed', where 'accidentally' comes from the Latin 'accidentalis', meaning 'happening by chance', and 'formed' from the Old English 'formian', meaning 'to shape or create'.

'accidentally' evolved from the Latin 'accidentalis' through Old French 'accidental', and 'formed' from Old English 'formian', eventually becoming the modern English 'formed'.

Initially, 'accidentally' meant 'by chance', and 'formed' meant 'to shape', which together still convey the idea of something shaped by chance.