from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A large tower or similar structure typically attached to a power plant through which water is circulated to lower its temperature by partial evaporation.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A large device, in the form of a tower-shaped building, in which warm water is cooled by evaporation caused by circulating currents of air
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a cooling system used in industry to cool hot water (by partial evaporation) before reusing it as a coolant
Sorry, no etymologies found.
You'd have a wooden thing they call a cooling tower and run the water through that to cool it off before it went into the pool.