from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A cup of coffee.
There is an attribution to Josephus Daniels (1862-1948) who, as Secretary of the U.S. Navy under President Woodrow Wilson in 1913, was said to have abolished the officers' wine mess. And thus coffee became the strongest drink aboard navy ships known as "a cup of Joe". (Wiktionary)