In versioning (e.g. software, documents, ...) a "version" or "revision" typically starts at 0 or 1 and increments with every change. The newest document is the one with highest version number.
I have a system where it is beneficial to do it the opposite way, newest document is saved as version 0 and the version of all the older documents is incremented. However, calling it a "version" may be misleading because it behaves opposite of the usual. Is there better word? Two words could work too.
Note that this is not something visible to the user, just trying to pick better term to use internally.