My GOD you are hardheaded!!!!! Nowhere in your mea culpa did you mention the symbology that is associated with this word.
I think it's been agreed that symbology (spell checker says that's not a word and offers no alternatives) comes AFTER language is in use.
You are just parroting what you have read that was written by a Greek-o-phile.
I can parrot you, "Straw man! Straw man!" You have no idea what those writers believe.
I doubt the authors of a page on peas are "Greek-o-philes" with vendettas against semitic root words. I think it's safe to assume that, when pisos, pisum, and pease, sound the same and mean the same thing, they are related. A word-to-word dictionary translation (i.e. pisos>pease) is about as objective as one can get.
When trying to find the beginning of language a good place to start is the roots of words. However, linguists on this forum don't think the roots are important. The well educated on this forum think it is enough to stop at the Greek/Latin form.
Sometimes that is all that's possible. If Greek adopted the word from some small unwritten regional language that went extinct 2500 years ago, it would be impossible to go back to that root.
You said that piss=peas. Since those words are different in Greek and Latin (and in English too, really), your symbolic connotations wouldn't have existed there and wouldn't have come to English.
Here is a perfect example of a lot of information and very little knowledge.
Pot calling the kettle block or peas calling the broccoli green, you know, whatever.