BOAC - I don't know. But this is what a throttle is:
https://en.wikipedia.org/wiki/Throttle
"What is often termed a throttle (in an aviation context) is more correctly called a thrust lever."
AutoThrust-Levers is a little long to say. I'm not sure of the reasoning or history behind calling them AutoThrottles - possibly since they can be in speed or thrust mode for a Boeing. Airbus calls it AutoThrust.