No, we're not...
we're right and
you're wrong! Michael Quinion is a noted etymologist and lexicographer...that is, an expert in the meaning and history of English words and phrases. He even worked on
The Oxford English Dictionary, recognised as the 'bible' in such matters.
If you click
here you will be taken to his web-page about 'cop', where you will see that he dismisses
your explanation as being 'spurious' and 'unlikely' and supports
our explanation.
I'm sure
xZetax wants the right explanation.