The iconic nickname, a “cup of Joe,” has several stories of origin. One legend concerns Josephus Daniels, the Secretary of the Navy during World War I. In 1914, he banned alcohol consumption on all U.S. Navy ships. Since coffee was the next strongest substitute, sailors sarcastically deemed it “a cup of Josephus,” but as that was a bit of a mouthful, the snarky nickname became shortened to just “a cup of Joe.
The Josephus Daniels story probably isn’t true. The term “cup of Joe” only appears in writing for the first time in 1930—long after the Navy’s ban on alcohol. Truthfully, the question “why is coffee called a cup of Joe?” has no clear answer. A much likelier theory is based on linguistics. This theory states that “Joe” is the simplified form of the word “jamoke,” which began as a nickname for coffee in the 19th century, a portmanteau of the coffee beans “Java,” and “mocha.” Therefore, “cup of jamoke” may have become shortened to a “cup of Joe.”
A third theory is based on the meaning of the word “Joe” in slang, as in “He’s just an average Joe.” This Joe refers to the common man on the street, a fellow, a guy, your neighbor who mows his lawn every Saturday at 8 a.m. (who we wish wouldn't drink coffee). A cup of Joe is therefore a way of saying “the common man’s drink.” Maybe that’s why all coffee lovers have these things in common.