Current translation for Withyham
  withy derived from wiðie  – a withy - willow band
  ham derived from hamm  – Denotes a piece of land surrounded with paling, wicker-work, etc., and so defended against water, which would otherwise wash it away, so a valley settlement or settlement with a jetty.
“Withy denotes a piece of land surrounded with paling, wicker”
Place name translation provided by saxonhistory.co.uk