i think it's from the recent origins mini they came out with to finally give him a solid origin, plus the weapon x history, not the mini by miller that had him getting his main chica back in japan (chocha is a powerful thing)
i remember long time ago, one of the xmen artist, the one responsible for helping to build the weapon x mythos, stated that marvel had no idea about his origin and the writers/artists were making it up as they went along, which helped raise his popularity but after a while all the contradictions, weird ass foolio shit, and being the only character without an origin people were getting pissed, hence the series.