Based on the provided source material, there is no information regarding a city named Olu in Wallis and Futuna. The source describes Olú primarily as a popular name among the Yoruba ethnic group.
In the Yoruba language, Olú is a diminutive of Olúwa, which translates to God, deity, or lord. While it is commonly used as a personal name, it also serves as a royal or noble title in specific regions of Nigeria, Benin, and Togo.