The words pottie, potty sound the same but have different meanings and spellings. Why do pottie, potty sound the same even though they are completely different words?
The answer is simple: pottie, potty are homophones of the English language.
Chiefly British Of little importance; trivial.
Chiefly British Slightly intoxicated.
Chiefly British Somewhat silly or crazy; addlebrained.
A small pot for use as a toilet by an infant or young child.
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.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").