The words wretch, retch sound the same but have different meanings and spellings. Why do wretch, retch sound the same even though they are completely different words?
The answer is simple: wretch, retch are homophones of the English language.
To try to vomit.
A miserable, unfortunate, or unhappy person.
A person regarded as base, mean, or despicable: "a stony adversary, an inhuman wretch” ( Shakespeare).
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.