It's actually Rhyming Slang for Rhyming Slang.
The correct rhyming slang for "Arse" is "Bottle & Glass"
but once people knew this the term couldn't really be used anymore without offending people. That prompted people to use the slang for "Bottle", which is "Aris-totle" as a slang for the first insult. "Aristotle" became "Aris" which in a London accent sounds the same as "Harris"
This has been in common London usage for well over a hundred years in it's current form.
"Do you wanna work overtime Dave?"
"Nah, stick it up yer Harris unless you're gonna offer time and a half"