The words crumby, crummie, crummy sound the same but have different meanings and spellings. Why do crumby, crummie, crummy sound the same even though they are completely different words?
The answer is simple: crumby, crummie, crummy are homophones of the English language.
Slang Variant of crummy.
Scots A cow, especially one with crooked horns.
Slang Miserable or wretched: a crummy situation in the family.
Slang Shabby or cheap: a crummy little rowboat.
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.