The Mesopotamians were the first to wine in wood containers but it was the Romans who first used white oak. It was the Roman's who noticed the unusual color of oak barrel staves stored in animal barns. The wood had darkened and ranged in color from honey to hazelnut to olive to black. The ammonia fumes, created from a mix of urine & hay, were interacting with the tannins found in white oak. What had been discovered was the very first fumed oak.
White oak is prized for wine barrels because the tannins in the wood can change the flavor of wine. Those same tannins react to concentrated ammonia fumes to alter the color of the wood.
Fumed oak allows the depth of the wood grain to show through. That look can't be duplicated by staining wood.