The words pampas, pompous sound the same but have different meanings and spellings. Why do pampas, pompous sound the same even though they are completely different words?
The answer is simple: pampas, pompous are homophones of the English language.
The extensive plains of South America south of the Amazon.
Characterized by excessive self-esteem or exaggerated dignity; pretentious: pompous officials who enjoy giving orders.
Full of high-sounding phrases; bombastic: a pompous proclamation.
Chracterized by pomp or stately display; ceremonious: a pompous occasion.
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.