Ethanol. The abbreviation comes from its molecular structure.
There are many kinds of alcohols. All of them have an Oxygen (O) and Hydrogen (H) molecule (thus the OH at the end of the term "ETOH.")
The type of alcohol is determined/named by the number of carbon molecules. The alcohol in intoxicating beverages has two carbon molecules. Anything with two carbons gets the prefix "Ethyl." So, the chemical is referred to as either Ethanol or Ethyl Alcohol, and is often just abbreviated "ETOH."
In a clinical context, "ETOH" as part of a history indicates chronic alcoholism. If you see "ETOH on board" or "positive ETOH" it means the patient is intoxicated at that time, i.e. a patient presents to the ED and the medics tell you "restrained driver involved in a two car MVC, positive ETOH."