Apprenticeships aren't very common in Jamaica any more, or maybe they are under a different name or in a different form. But it used to be routine that a young person could go "learn a trade"- and this meant working as an apprentice to a tailor or mechanic or so. Case in point, Marcus Garvey left his home in St. Ann and went to work as an apprentice for a printer in Kingston. Nowadays you learn a trade in high school or at a post secondary vocational institution, most often something under the umbrella of HEART Trust/NTA.
Well, back in the day, some unscruplous persons would take an apprentice under their wings, with the sole purpose of extracting as much cheap labour from them as possible. The way to drag out the training period was to teach the poor apprentices little or nothing, so what they would do was just have them do tasks that required no skill at all, like hand me this tool, or deliver that package, or hold this thing. Yes, "Hold this" is standard English for ole ya.
Over time, "ole ya" became rich with meaning. For instance a person who spent ages as an apprentice but never actually acquired mastery of the trade got called Ole Ya. If someone underestimated your ability by constantly assigning you tasks that did not require much intelligence, you might begin to think they were taking you for Ole Ya.
I'm laughing but it's not funny. Lots of talented people never really scale any great heights, and end up as Ole Ya for years and years and years, sometimes a whole lifetime. The reasons must be complex and depend on all sorts of situations, but still take a shot at it and tell me why.