Bathtub gin

Bathtub gin refers to any style of homemade spirit made in amateur conditions. The term first appeared in 1920, in the prohibition-era United States, in reference to the poor-quality alcohol that was being made.
As gin was the predominant drink in the 1920s, many variations were created by mixing cheap grain alcohol with water and flavorings and other agents, such as juniper berry juice and glycerin. In addition, mixing grain alcohol, water, and flavorings in vessels large enough to supply commercial users had to be small enough for the operation to go undetected by the police. The common metal bathtub in use at the time would have been ideal as would have been a ceramic bathtub, hence the name, 'bathtub gin'. However, since distillation requires closed distillation apparatus and cannot be accomplished in an open vessel such as a bathtub, stories of distilled alcoholic products produced in an open bathtub are likely untrue.
Many gin cocktails owe their existence to bathtub gin, as they were also created in order to mask the unpleasant taste.
Bathtub Gin is also the name for a gin brand produced by Ableforth's in the United Kingdom. Although not made in a bathtub, it is produced using compounding/infusing rather than using botanical distillation.
In popular culture.
In the 1939 film "The Roaring Twenties" Eddie Bartlett, played by James Cagney, is seen mixing a large can of grain alcohol with water in a bathtub to produce bootleg gin during the prohibition era.
In the 1969 film "Model Shop", in the Lola's house there is a big Bathtub gyn poster on the wall.
In the 1982 film "Annie" Miss Hannigan, played by Carol Burnett, is shown doctoring bathtub gin.
The band Phish song "Bathtub Gin" was released on the 1990 album "Lawn Boy". The song also appears on "Hampton Comes Alive" (1999) and several other live albums.
The "Simpsons" 1997 episode "Homer vs. the Eighteenth Amendment" features Homer and Bart mixing and brewing alcohol, including gin, in various bathtubs in the basement and secretly supplying and distributing it to Moe's Tavern via an elaborate delivery system to avoid detection.
In the 2018 film "Mary Poppins Returns", starring Emily Blunt, Mary Poppins sings "flap about in bathtub gin" during a song while swimming in a bathtub with the Banks children.