The words trustee, trusty sound the same but have different meanings and spellings. Why do trustee, trusty sound the same even though they are completely different words?
The answer is simple: trustee, trusty are homophones of the English language.
Law One, such as a bank, that holds legal title to property in order to administer it for a beneficiary.
A member of a board elected or appointed to direct the funds and policy of an institution.
A country responsible for supervising a trust territory. See Usage Note at -ee1.
To place (property) in the care of a trustee.
Meriting trust; trustworthy. See Synonyms at reliable.
A convict regarded as worthy of trust and therefore granted special privileges.
A trusted person.
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").