means A rapidly rotating mass of water, usually formed where opposing currents meet, that pulls nearby objects toward its spiraling center.

from A plain English compound, welded from "whirl" — to spin or turn rapidly, related to Old Norse "hvirfla" and a cousin of "whirligig" — and "pool," a body of still or eddying water from Old English "pol." So the word is exactly what it says on the tin: a pool that whirls. The "whirl" half carries that dizzy, onomatopoeic sound of motion, the kind of word that spins a little in the mouth before you've even finished saying it.