Mayo is a four letter word.
Just to be clear, thats the Spanish word "Mayo", pronounced my-o. Not to be confused with the white condiment.
Today is Cinco de Mayo, May fifth, and is a holiday that commemorates the Mexican victory at the Battle of Puebla in 1862 over the invading French army. The victory was also something of a surprise - the Mexican army was undermanned and underpowered compared to the French. In defeating the French, they halted French plans to extend their empire in the Americas and provided a major boost in morale to the Mexican people.
The victory, however, was relatively short-lived. A year later, a much larger French force finally deposed the Mexican government and installed their own government over Mexico. Within three years, however, Mexico had again fought off European conquerors and re-established her independence.