Fennel
It was called a Watt after James Watt born 19 January 1736
Greenock, Renfrewshire, Scotland, United Kingdom. He was an important pioneer of steam engine power.
The watt (abbreviated W) is the International System of Units' (SI) standard unit of power (energy per unit time), the equivalent of one joule per second.
"The watt is used to specify the rate at which electrical energy is dissipated, or the rate at which electromagnetic energy is radiated, absorbed, or dissipated."
Which is about as far as my physics knowledge goes.
The higher the number of Watts quoted on the base of your kettle the quicker it will boil any set volume of water. Look at the watts on the base of your kettle, (but do empty it first. )
I always go for a 3KW rating (3000 watts.) They are more expensive but much quicker .