The term "Secret Squirrel" began as a cartoon character parodying the spy genre and has since evolved into a colloquial term within military and intelligence circles to describe classified or covert activities and personnel.

"Secret Squirrel" is a cartoon character created by Hanna-Barbera. The character first appeared in the early 1960s as part of "The Atom Ant/Secret Squirrel Show," which was a syndicated television program.

The show is a parody of the spy genre that was very popular during the Cold War era, especially with the rise of spy films and television shows like James Bond.

Secret Squirrel is depicted as a James Bond-esque secret agent, complete with a trench coat, hat, and various spy gadgets. He works for a secret organization and undertakes missions to thwart the plans of various villains.

In the military, "Secret Squirrel" has come to refer colloquially to activities, personnel, or missions that are classified or highly secretive. It is often used humorously or affectionately to describe individuals involved in clandestine or covert operations. For example, intelligence officers, special operations personnel, or anyone working on a "need-to-know" basis might be referred to as "Secret Squirrels."