The words cash, cache sound the same but have different meanings and spellings. Why do cash, cache sound the same even though they are completely different words?
The answer is simple: cash, cache are homophones of the English language.
A hiding place used especially for storing provisions.
A place for concealment and safekeeping, as of valuables.
A store of goods or valuables concealed in a hiding place: maintained a cache of food in case of emergencies.
Computer Science A fast storage buffer in the central processing unit of a computer. Also called cache memory.
Money in the form of bills or coins; currency.
Payment for goods or services in currency or by check.
To exchange for or convert into ready money: cash a check; cash in one's gambling chips.
cash in To withdraw from a venture by or as if by settling one's account.
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.