'debriefing' originates from the verb 'debrief', which combines the prefix 'de-' meaning 'reverse' or 'remove' with 'brief', meaning 'to inform'.

'debrief' evolved from the practice of 'briefing', where 'brief' meant to give instructions or information. 'Debrief' thus came to mean the opposite, to gather information after the fact.

Initially, it meant 'to remove or reverse briefing', but over time it evolved into its current meaning of 'gathering information after a task'.