Middle Dutch boke "blow," Middle High German bochen "to slap," buc "blow," "stroke," Danish bask "hit"
[O]f unknown origin ; perh. related to an OTeut. *boki- ... but in this case the formation remains unexplained. It has also been compared to Danish bask blow, stripe, but no intermed. links have been found. (More probably it is of native English origin ...). ~ Sir J. A. H. Murray, A New English Dictionary on Historical Principles (1887)