Wallop

British slang for beer dates from the early 20th century (the OED gives 1936), rarely heard these days but was popular just before and after WWI; inspired by an earlier meaning of wallop that dates from the early 18th century and means to flounder or make clumsy, uncontrolled movements, as one would after a few pints of wallop. Wallop meaning to thrash or beat soundly dates from the early 19th century. See also codswallop.