It's a play on a famous Zen Haiku about a samurai warrior that was sitting under a potato tree when a spud fell on his head thus discovering reverb.....
Verrrrry heavy reverb. Approximately 2000 lbs of reverb in fact.
"Gravitaton (noun): A unit of measurement for the strength of reverberation in a space, equivalent to 2000 pounds of reverb. The term "gravitaton" derives its name from the way in which the intense, deep vibrations of sound waves can create a feeling of weight and gravitational pull in a room.
For example, if a musician were to perform in a space with particularly strong reverberation, they might say "Wow, this room has at least 10 gravitaton of reverb!" This would indicate that the sound waves in the room are particularly intense and have a powerful, immersive effect on the listener."