If you want to eat a _____ sandwich in your life again....

X, is finely shredded cabbage that has been fermented by various lactic acid bacteria, including Leuconostoc, Lactobacillus, and Pediococcus.
It has a long shelf-life and a distinctive sour flavor, both of which result from the lactic acid that forms when the bacteria ferment the sugars in the cabbage.
It is therefore not to be confused with coleslaw, which receives its acidic taste from vinegar.
X is considered to be the origin of a slang term. Identify the slang.