I work in a coffeehouse and a customer and myself are stumped with the origin of the phrase ‘cup of joe’.  Any ideas would be greatly appreciated.
User Detail :  
Name : Aaron E., Gender : F, Sexual Orientation : Lesbian, Race : White/Caucasian, Religion : Agnostic, Age : 24, City : Dallas, State : TX, Country : United States, Occupation : coffeemaker/ student, Education level : 2 Years of College, Social class : Lower middle class,