Bottle Logic is a synonym for a FIFO unload routine. It comes from the song that school kids sing to annoy their bus drivers on field trips.
Ninety nine bottles of beer on the wall,
Ninety nine bottles of beer.
Take one down and pass it around,
Ninety eight bottles of beer
Ninety eight bottles of beer on the wall,
Ninety eight bottles of beer.
Take one down and pass it around,
Ninety seven bottles of beer...
etc, etc, ad infinitum.