Do you drink Joe?

Have a cup of joe... why? call coffee, joe? Well this was the best answer I cam across with...

The Word Detective ( http://www.word-detective.com/041899.html ) is pretty much in agreement. WorldWideWords agrees with the Word Detective, who suggests that "joe" as slang for coffee might be derived from "Joe" as a synonym for "the common man," as in "regular joe." They do differ on whether "GI Joe" for enlisted men was in use at that ttime. Even if it wasn't, US citizens jhad been using "the common Joe" and other such phrases for a whle when the ft instance of joe for coffee is written.