Food historians offer four possible theories for the origin of mayonnaise. The most popular story dates to June 28, 1756, when the French Duke Richelieu captured Port Mayon on the Spanish island of Minorca. When preparing the victory feast, the duke's chef was forced to substitute olive oil for cream in a sauce. Unexpectedly pleased with the result, the chef christened the result "mahonnaise" in honor of the place of victory.