Jiggery pokery is a spell that is used to frighten muggles, to the point of causing them to run, screaming and tripping, away.
Jiggery-pokery is a British term meaning "underhand or deceitful behaviour".
Behind the scenes
- It is never outright stated that this is a spell, although it is written in italics as with other spells and immediately after Dudley begins running, screaming and tripping, so it is a reasonable assumption to assume it is.
- Harry Potter and the Chamber of Secrets (First appearance)