The words wailer, waler, whaler sound the same but have different meanings and spellings. Why do wailer, waler, whaler sound the same even though they are completely different words?
The answer is simple: wailer, waler, whaler are homophones of the English language.
One who wails or laments.
A hired (professional) mourner.
A light saddle horse of mixed breed imported from Australia.
One that hunts or processes whales.
A whaling ship.
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.