Any time you hear the word "buttload" as an amount, you know it mean a lot. But it turns out that it really does mean a specific amount, and that amount is... a lot.
After immediately falling down a Google hole about it, I discovered that this is, indeed, true! A butt, also known as a pipe, is a unit of measure for English Brewery Cask Units and English Wine Cask Units. It's the second-largest barrel size, equal to half a tun, which was typically 252 Imperial Gallons (although that exact quantity has changed throughout history; current standards place an English Tun at 259 US gallons or 216 Imperial Gallons).
You have to admit that 129 gallons is a substantial amount of beer or wine. That's enough for the kind of party the police would want to speak to you about. Read more about beer and wine measurements with plenty of links to follow at Boing Boing.
(Image credit: Grolltech)