As with many spirits around the world, in the early days, rum producers rarely bottled and sold their own wares, other than to locals and those who travelled to them. Instead, they would sell rum by the cask and it, in turn, would be sold on, a commodity in a worldwide market.
However, as with all commodities, there needs to be a final buyer – the rum drinker. The final steps before rums would reach the drinker often involved blending. Rum merchants with casks from all over the world would combine those rums to create the consistent bottlings that their clients required, tasting the same (or at least similar) to the last bottle they bought. The reputations of the rum traders depended on their blends, with names like Doorly's and Myer's continuing across the decades thanks to the trust drinkers have placed in them to produce good blended rums.
Those original rums would have been what we call Blended Traditionalist Rums – rums blended only from traditional pot-still and traditional column-still rums, the old-fashioned styles of rum that laid the ground work for the world's love of the spirit today.