booby trap

From booby (“dunce, idiot”).

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booby trap (plural booby traps)

1. (military) An antipersonnel device deliberately hidden or disguised as a harmless object.
2. A practical joke by which something is made to fall upon someone entering through a door, or the like.
3. (by extension) An unforeseen source of danger; a pitfall.

• boobytrap

• canary trap
• honeypot
• IED

• (practical joke): 1873, John Camden Hotten, The Slang Dictionary