@James34,
Hi James.
I've been able to find SHIVE as a bung for wide necked bottles, but not casks.
The other definition I found for shive is what you have described as a spile. A shive is a wooden or plastic fitting in a cask to allow the cask to be cleaned and refilled, and to control the level of carbon dioxide. A spile is a plug that goes into a shive.
I hope that makes sense.