Have you not answered your own question? OT does indeed stand for Operational Transformation.

https://en.wikipedia.org/wiki/Operational_transformation

"Operation Transformation" = "a system that supports collaboration functionalities by separating the high-level transformation (or integration) control from the low-level transformation functions"

Source: OT's Wikipedia article

But I felt the same. Never heard of "Operation Transformation" before and both OT and its alias were equally opaque to me.