The words copt, copped sound the same but have different meanings and spellings. Why do copt, copped sound the same even though they are completely different words?
The answer is simple: copt, copped are homophones of the English language.
Simple past tense and past participle of cop.
Rising to a point or head; conical; pointed; crested.
An Egyptian belonging to or descended from the people of ancient or pre-Islamic Egypt.
A member of the Coptic Church.
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.
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").