'truth-telling' originates from the combination of 'truth' and 'telling', where 'truth' means 'factual' and 'telling' means 'narrating or stating'.

'truth' and 'telling' have been used in English since the Middle Ages, and their combination as 'truth-telling' has been used to emphasize the act of narrating facts.

Initially, it meant 'narrating facts', and this meaning has largely remained the same in modern usage.