I decided to look it up in my massive great Oxford English Dictionary and there I discovered that a bonce was originally a type of large marble; the word is first recorded in the 19th century but nobody knows its origin. The OED cites two examples of its use as a slang term for 'head': in 1909, somebody called R.
Why is it called a bonce?
The original bonce was a large marble that featured in several children's games of the nineteenth century. The English Dialect Dictionary suggests it's a version of bounce, since such a marble was also called a bouncer and was “the large earthenware marble used for bouncing or playing with checks or cubes”.
Is bonce another word for head?
Your bonce is your head.
