The words deviser, devisor, divisor sound the same but have different meanings and spellings. Why do deviser, devisor, divisor sound the same even though they are completely different words?
The answer is simple: deviser, devisor, divisor are homophones of the English language.
A person who devises; a planner.
Law One that makes a devise.
The quantity by which another quantity, the dividend, is to be divided.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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.