A person who studies the origin of the words and its meaning is called an etymologist. Etymology is a branch of linguistics. I think all these are terms are named in English language, in every developed language there is a different term for each studies.
The wisdom of using an electric heater depends on the per kilowatt cost in your region. 1  If your heater has a 1000 watt rating and your cost of electricity is $0.15/Kwh your cost to operate for one hour would be $0.15. 2  If the element is activated 10 hours out of every 24 hours your cost per day would be $1.50.
The cost of electricity is about 14p/kWh, which means that it would cost about 45p to run a 3kW immersion heater for an hour. Normally though the immersion will turn on and off via the thermostat so the amount of time they are on fluctuates, depending on the existing temperature of the water in the hot water tank.