The phrase "drunk as a skunk" is thought to have originated in the United States in the 19th century. Skunks are known for their pungent odor, which is caused by a chemical called butyl mercaptan. This chemical is also found in certain alcoholic beverages, such as whiskey and brandy. It is thought that the comparison between the smell of skunks and the smell of alcohol led to the phrase "drunk as a skunk."
Another possible origin of the phrase is the fact that skunks are nocturnal animals, and they are often seen stumbling around in a disoriented state when they are awake during the day. This behavior is similar to the behavior of a person who is drunk.
Regardless of its exact origin, the phrase "drunk as a skunk" is a common idiom that is used to describe someone who is very drunk.