The words gofer, gopher sound the same but have different meanings and spellings. Why do gofer, gopher sound the same even though they are completely different words?
The answer is simple: gofer, gopher are homophones of the English language.
Slang An employee who runs errands in addition to performing regular duties.
Any of various short-tailed, burrowing rodents of the family Geomyidae of North America, having fur-lined external cheek pouches. Also called pocket gopher.
Any of various ground squirrels of the genus Citellus of North American prairies.
Any of several burrowing tortoises of the genus Gopherus, especially G. polyphemus of the southeast United States.
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.