from
http://answers.yahoo.com/question/in...3083133AAYPZtN
The exact origin of the phrase is unknown, but etymologists suspect it is a childish corruption of a phrase that would have made more sense in the Hide-and-seek context; such as "all ye, all ye, oxen free!", "all in free", "out’s in free", "all set free", "All ye all ye outs in free", "All ye, all ye, outs are free", or "All the, all the outs in free"; or possibly a corruption of the German "Alle, alle auch sind frei", (literally, "Everyone, everyone also is free").
Originally Posted by Loretta
What DOES oly-oly-oxen-free mean? Curious minds want to know!