Wiht is an Anglo-Saxon word meaning 'rise' or 'rising' and was translated as Vectis in Latin.
Umm... Ptolemy's Geography already called the Isle Wight Vectis only about a century after Roman occupation, long before any (known) Saxon king.
Tacking back to a place we've been before: on the subject of the Isle of Wight, Roman-Britain.org says There is an oft-quoted passage by the great polymath Pliny the Elder (Natural History Book XVI, verse 104) dating to the late 70's AD which names the island Mictis as the centre of the British tin trade, stating that it lay off the south coast of Britain some six days sail from Gaul. This name has often been mistakenly associated with the Isle of Wight, but is now known to refer to Saint Michael's Mount off the Cornish coast opposite Marazion, known in ancient times as Ictis.
Wilkens mentions St. Michael's Mount as the centre of the tin trade, but I dunno whether he read it or postulated it.
, Roman-Britain.org says: St. Michael's Mount was widely known as a port and trading market from very early times. Prehistoric traders passing between the western parts of Britain and the Continent would not have wished to risk the rough and dangerous voyage around Land's End, and so sent their cargoes across the narrowest and most level part of Cornwall from the Hayle estuary to St. Michael's Mount.
Wilkens locates Scylla and Charybdis around there, which were perilous to pass. The Hayle is where St. Ives is, per an earlier discussion.