butter (“A soft, fatty foodstuff made by churning the cream of milk”) + fingers (“One of the long extremities of the hand”), suggesting that someone is clumsy and drops things because their hands are coated in slippery butter.
butterfingers (plural butterfingers)
- someone who is clumsy or uncoordinated; a klutz; someone who tends to drop things
- I am such a butterfingers. That's the third drink I've spilled today.