A booby trap is a device or setup that is intended to kill, harm or surprise a human or another animal. It is triggered by the presence or actions of the victim and sometimes has some form of bait designed to lure the victim towards it. The trap may be set to act upon trespassers that enter restricted areas, and it can be triggered when the victim performs an action (e.g., opening a door, picking something up, or switching something on). It can also be triggered by vehicles driving along a road, as in the case of improvised explosive devices (IEDs).
Booby traps should not be confused with mantraps which are designed to catch a person. Lethal booby traps are often used in warfare, particularly guerrilla warfare, and traps designed to cause injury or pain are also sometimes used by criminals wanting to protect drugs or other illicit property, and by some owners of legal property who wish to protect it from theft. Booby traps which merely cause discomfort or embarrassment are a popular form of practical joke.
The Spanish word bobo translates to "stupid, daft, naïve, simple, fool, idiot, clown, funny man, one who is easily cheated" and similar pejorative terms. The slang of bobo, bubie, translates to "dunce". Variations of this word exist in other languages (such as Latin), with their meaning being "to stammer".
In approximately 1590, the word began appearing in the English language as booby, meaning "stupid person, slow bird". The seabird in question was the genus Sula, with their common name being boobies. These birds have large flat feet and wide wingspans for marine habitats but are clumsy and slow on shore making them easy to catch. The birds are also known for landing aboard seagoing vessels, whereupon they have been eaten by the crew.
The phrase booby trap originally applied to schoolboy pranks, but took on its more serious connotation during World War I.
A military booby trap is designed to kill or injure a person who activates its trigger, or employed to reveal the location of an enemy by setting off a signalling device.