The words whirl, whorl sound the same but have different meanings and spellings. Why do whirl, whorl sound the same even though they are completely different words?
The answer is simple: whirl, whorl are homophones of the English language.
To revolve rapidly about a center or an axis. See Synonyms at turn.
To rotate or spin rapidly: The dancer whirled across the stage.
To turn rapidly, changing direction; wheel: She whirled around to face him.
To have the sensation of spinning; reel: My head is whirling with data.
A form that coils or spirals; a curl or swirl: spread the icing in peaks and whorls.
Botany An arrangement of three or more leaves, petals, or other organs radiating from a single node.
Zoology A single turn or volution of a spiral shell.
One of the circular ridges or convolutions of a fingerprint.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.