[reaperducer]

for some reason resident debuggers were frequently called monitors in early microcomputing

I think it's more like "for some reason, monitors are called debuggers in later microcomputing."

[irishcoffee]

Debuggers were people pulling bugs out of walls of vacuum tubes. They monitored and literally debugged a computer. Monitor made more sense at first, they monitored for bugs.

At least, this is my understanding.