Following the establishment of the cavalry division of the imperial army of Old Oyo in about the 17th century, the dynasties of Eso chieftains that developed out of it in the metropolitan town of Ikoyi became famous over time for a manner of conduct that came to be synonymous with the noble titleholders themselves.
Following the disbanding of the cavalry itself in the 19th century, the children and grandchildren of its former members began to use its name as an affirmation in a manner similar to the usage of the Latin dictum infra dignitatem.
Seeing as how a classical Eso was both traditionally obligated and widely considered to be noble in both word and deed, stating that you were a descendant of such a personage was seen within this culture as a means of subconsciously causing yourself to live up to his legacy.
The phrase therefore could variously symbolize your contempt for anything mean or low, or your scorn for difficulty, danger or - potentially - death itself.
By stating that you were a child of an Eso, you were effectively declaring that you knew no fear, or that a particular thing was beneath your dignity.