The words whir, were sound the same but have different meanings and spellings. Why do whir, were sound the same even though they are completely different words?
The answer is simple: whir, were are homophones of the English language.
Second person singular and plural and first and third person plural past indicative of be.
Past subjunctive of be. See Usage Notes at if, wish.
To move so as to produce a vibrating or buzzing sound.
To cause to make a vibratory sound.
A sound of buzzing or vibration: the whir of turning wheels.
Excited, noisy activity; bustle: the whir of busy shoppers.
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.