I believe
Withernam is not a place but a Middle English legal term, for a form of reprisal action. See here ...
https://quod.lib.umich.edu/m/middle-english-dictionary/dictionary/MED53047Much of this recites action that has already happened in the past. I don’t claim to have every word of it (especially towards the end), but I think it goes something like this:
The king had ordered the sheriff of Kent to restore to John Heth his cattle, which William Bollyng had taken and unjustly detained. But the sheriff didn’t do this and didn’t explain why, so he was upbraided for being in contempt of the king’s orders and for causing damage to John Heth.
John has now turned up in court, but William has not come. The sheriff now reports that William took John’s animals so far off that they could not be found. The sheriff is now ordered to seize William's cattle as a form of reprisal (called 'withernam') and to keep the cattle until William returns John's cattle. The sheriff is to report back to the court, and a date is set for the next hearing.
(Afraid I don’t have time to do the second one right now.)