Schläfer

Schläfer is a German noun that literally means a person who sleeps. The word derives from schlafen (to sleep) with the agentive suffix -er, a productive derivation in German. In everyday language, Schläfer denotes someone who is asleep, but it can also be used metaphorically to describe someone who remains inactive, hidden, or inconspicuous for an extended period.

In intelligence and security contexts, Schläfer is used to refer to a sleeper or sleeper agent—an operative placed in a target country or organization who remains dormant and concealed until activated by orders. The concept appears in discussions of espionage history, counterintelligence, and in popular media.

In culture and media, Schläfer can occur as a character name, title, or descriptor in novels, films, or games, depending on the work. It is also a surname in German-speaking regions.

Notes: The English cognate sleeper shares its etymology with Schläfer. The term Schlafwandler refers to a sleepwalker and is related linguistically but distinct in meaning. The usage of Schläfer is generally neutral, with connotations driven by context.