from The Century Dictionary.
- noun In electricity, a coil of wire arranged so as to be capable of rotation in a magnetic field, and connected with a galvanometer by means of which the induced current of electricity can be measured. It is used for measuring the strength of magnetic fields as compared with that of the earth.
Sorry, no etymologies found.
It was 1927 before technology caught up with the prize, notably the development of the nine-cylinder, air-cooled Wright Whirlwind engine and the earth-inductor compass, the first providing more reliability and the second more accuracy than before.
A Race Across the Pond Dan Ford 2011