Make me wonder what a "scuttle butt" really is...
The butt is basically a barrel - often filled with water and secured to a mast by ropes. OED says a scuttle is "a platform at the head of a lower mast, a top."
A couple of sailors could meet at the water butt, ostensibly to drink, and exchange or pass along gossip or conversations they overheard between officers without arousing the officers' suspicions - hence "scuttle butt" meaning unsubstantiated gossip.
OED says the scuttle - in cars - is the area between the windscreen and the bonnet. Any help?