swish: The liquor leached from oak barrels procured from distilleries (usually whiskey). The barrels were purchased ostensibly for making flower pots, but first, the custom was to fill ’em up with distilled water and let the alcohol leach out. The resulting spirit was referred to as “swish.” Sometimes it would burn with a blue flame, as long as no one else had been to the barrel first.
exempli gratia: “We’d put the swish in glass jugs and when company came over, plunk it down in the middle of the table. It was strong stuff.”
N.B. This has been done by people I know within recent memory.