The words hippie, hippy sound the same but have different meanings and spellings. Why do hippie, hippy sound the same even though they are completely different words?
The answer is simple: hippie, hippy are homophones of the English language.
A person who opposes and rejects many of the conventional standards and customs of society, especially one who advocates extreme liberalism in sociopolitical attitudes and lifestyles.
Variant of hippie.
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").