'customarily-formed' originates from the English word 'customary,' which comes from the Latin word 'consuetudinarius,' where 'consuetudo' meant 'habit or custom.'

'customarily' evolved from the Middle English word 'custumary,' which was derived from the Old French 'costumier,' and eventually became the modern English word 'customarily.'

Initially, it meant 'formed according to custom,' and this meaning has largely remained the same in modern usage.