'off-script' originates from the English words 'off' and 'script', where 'off' meant 'away from' and 'script' referred to a written text or plan.

'off-script' evolved from the combination of 'off' and 'script', used in theatrical contexts to describe actors deviating from their lines.

Initially, it meant 'away from the written text', but over time it evolved to mean 'deviating from any planned course of action'.