Latin buttis "cask". Bottle is related. A storeroom of casks of wine was called a buterie, and that is where the U.K. English term buttery "food shop in a college" comes from

and butter is made in a churn or cask. But wait for it.. the entymology is the other way round!!. Ignore the "in reply to"
In reply to:

: butter. Middle English, from Old English butere, from Latin butyrum, from Greek boutyron, from bous cow + tyros cheese; akin to Avestan tuiri- curds -- more at COW

from Miriam-Webster via yourdic (I knew him Horatio)
Rod