Oly Oly Oxen Free

Oly Oly Oxen Free is a six note, seven beat tone used as an all clear code by the SPARTAN IIs. They learned it from Deja on Reach when they were younger and have used it ever since.

Psychology
Oly Oly Oxen Free was a secret amongst the Spartans; none but they and a select few outsiders knew it. Those outsiders were close to the Spartan family; such as Dr. Catherine Halsey, Cortana, and Sergeant Johnson. Thus, the signal was extremely important to each Spartan; they would rather die than give up the significance of the tone, which could be used to betray or endanger their teammates.

Uses
Oly Oly Oxen Free was used on numerous occasions throughout Halo: The Fall of Reach and Halo: First Strike. Some of the times it was used are:


 * After the Spartan Team had beaten Tango Company, and John-117 had checked to make sure their evacuation point was all clear.
 * After The Battle of Reach, Anton-044 used it as an S.O.S. signal over the E-Band.
 * For the Spartans to enter CASTLE Base, Kelly-087 used it to let Dr. Halsey know it was them.
 * During Operation: FIRST STRIKE, Linda-058 used it to let John know where she was so he could pick her up.
 * At the end of Operation: FIRST STRIKE, Sergeant Johnson used it to let Blue team know where the Gettysburg was holding station behind a nearby asteroid.

Links

 * Spartan Language

Trivia
People genrally say "Oly Oly Oxen Free" when they want to quit a game.