Linked from
The 21 pages that link to Watt, each with the reason it gives.
JouleRelated: Power specifies how quickly joules are transferred.
James WattRelated: The unit was named for Watt in recognition of his contributions to steam power.
DecibelRelated: Absolute power levels such as dBm specify a reference in watts.
Radiant fluxRelated: Radiant flux is expressed in watts because it is a rate of energy transfer.
IrradianceRelated: Irradiance uses watts to express incoming radiant power.
Luminous efficacyRelated: Watts measure the input power in the efficacy denominator.