Blacksheep,
I think the history of the 80kts call dates back to a tailwheeled Boeing bomber (B17?). It was the speed that the pilot pushed the control column forward to get the tailwheel off the ground. This tradition (as well as using the same style of control column) continued with every Boeing aircraft thereafter.
It certainly is a Boeing thing, on a British civil jet with more than two engines but less than 4 we called 100kts.