writing style - Is 'Oxford Comma' Capitalised?

I was taught in primary school that a common noun refers to a thing, idea, person, etc. whereas a proper noun refers to a specific thing, idea, person, etc. and that when referring to specifics and proper nouns, the words were always capitalised.

The way I see it, the Oxford comma is a specific type of a thing (comma), hence a proper noun, ergo capitalisation for both words.

A theoretical example of this is Tom's ball. If Tom owns a ball, it is not capitalised. However, when he prints a new pattern on many balls of the same variety and gives them to his friends, he would call it a Tom Ball, rather than a Tom ball, right?

Why is this not the case for the Oxford comma, seeing it is not Oxford's comma?

I would appreciate if you could also make reference to the example I used in the question in your answer to further assist me in understanding.