(informal)knock (someone) into a state of unconsciousness, confusion or disarray. Possibly from an old sailors' game "building the galleass" (galleass: a wargalley) where a new sailor (the victim) would be hit in the face with a mop dipped in a slop bucket knocking him "galleass" (to the deck of the galleass). —SHSBC Binder 29 Approved Glossary