Today I learned

To clarify, a scuttle is a window cut in the side of a shop to allow for airflow and light. To scuttle a ship is to make more of them, only these ones let in water.

A scuttlebutt was a butt (a cask) that had been scuttled, ie a hole cut in it so water could be drawn out. Just like the modern water cooler, the scuttlebutt was where sailors exchanged gossip, so it's now synonymous with "the latest rumors."