What is the simple subject of this sentence The origin game chess not well known?

The simple subject of the sentence "The origin of chess is not well known" is origin.

Here's why:

* Subject: The subject of a sentence is the person, place, or thing that performs the action of the verb.

* Simple Subject: The simple subject is the main noun or pronoun that performs the action of the verb.

In this case, the verb is "is" and the origin of chess is the thing that is not well known.