is a Japanese slang term for testicles, similar in use and concept to the English slang "family jewels". Sometimes it is used in the back slang form, .
Use of the term has been traced back to the Edo Period.[1] According to folklore, the has magical shapeshifting abilities, including their oversized scrotums (as depicted in art), which the animals could use in multiple ways. In addition, the skin of the was used traditionally by workers in Kanazawa for the production of gold leaf, linking gold to and, by extension, testicles.[2] [3]