Associative Array hash Alias of ((hash|Hash)) It seems "Associative" is because the hash can take out the value of an arbitrary key, and "Array" is because you can assume it to be an array which the subscript is not number. Once upon a time, the associative array (called associative memory then) was thought to be realized with hardware, but improvement of hardware's calculation speed and discovery of an appropriate algorithm (it is called "((Hash)) table", derivation of the hash) brought us achievement only with software.