During the Battle of Britain, radar operators faced a maddening problem: they could see blips on the screen, but they could not tell friend from foe. The solution was IFF—Identification Friend or Foe—a system in which friendly aircraft, when pinged by radar, answered back with a coded signal. The British code-named the airborne component "Parrot." Ground controllers began telling pilots to "squawk your Parrot" when they wanted the identification signal turned on, and to "strangle your Parrot" when silence was required. The bird's name faded after the war; the verb remained.

The wartime IFF Mark III, introduced in 1943, operated on a dedicated frequency band of 157–187 MHz and used a transponder to reply to ground interrogators. This secondary radar concept—aircraft answering a challenge—was the direct ancestor of the civil transponder. When commercial aviation expanded after 1945, the technology migrated to the air traffic control system, but the old command endured. Today, when a controller says, "Squawk 7421," the pilot is being asked to set a four-digit octal code on the transponder, drawn from 4,096 possible combinations.

Certain codes carry silent weight: 7700 for general emergency, 7600 for radio failure, 7500 for unlawful interference. They are spoken in the same clipped shorthand that was forged in the heat of war, when a missed blip might mean a Spitfire or a Stuka. The parrot is gone, but the squawk remains.