The word "cast" has been in the English language for quite a long time, while the word "caste" comes after. The cast was taken from the Proto-Germanic, while caste was derived from the Spanish and Portuguese language. The word caste is specific, and it has only possible meaning.
The meaning of the word can be said to be a class or group in a society which interacts majorly with each other. When there are two or more of it in a society, it is referred to as a caste system. Caste can actually be hereditary. On the other hand, the word cast can be in the form of a noun or verb, and it has several meanings.
One basic meaning of the word when it appears as a verb is "to throw," and it can also mean "to discard" or "to move away." The word cast is also usually used when referring to performing a magical spell. "Cast" as a noun is mainly used to refer to the shaping of an object.