Definition of the word bug out

The expression "bug out" originated during World War II in the US Army as slang for quickly retreating or abandoning a military post under enemy attack or when faced with an untenable situation. The term "bug" was used colloquially to denote a mechanical fault, malfunction, or problematic insect, hence "bug out" conveyed the sense of a rapid and abrupt departure, much like a malfunctioning device or irritating insect. The use of "bug out" as a contemporary survivalist idiom to describe leaving a habitation or geographic area rapidly, often with a high degree of urgency, such as during a cataclysmic event or extreme danger, is an adaptation of the military jargon.