From the essay Programming Languages Explained by Paul Graham, published in Hackers & Painters:
The high-level language that you feed the compiler is also known as source code, and the machine language translation it generates is called object code.
Object code, or sometimes object module, is what a computer compiler produces.
Traditionally, the output of the compilation has been called object code or sometimes an object module. (Note that the term "object" here is not related to object-oriented programming.)
So what is the term object related to?