The first mention of the names of the Channel Islands occurs in the Antonine Itinerary from Portsmouth to Ostia. Starting from Portsmouth we are given:
Riduna = ritu, 'ford' now Tatihou, Dadhi|holm (the island is reachable on foot at low tide)
Sarmia = sar, 'current' now Alderney/Aurigny, alda|renna|ey, 'wave-running-island' (Alderney is in the Raz Blanchard a very strong tidal race)
Caesarea = kai, 'clear, bright green' now Guernsey, groen|ro|ey, 'green-corner-island' (seen from the sea before urbanisation, the lowest part of the island was bright green, standing out against the higher, dun coloured dunes and the dark wooded hills)
Barsa = barro, 'mount' now Jethou, jot|holm, 'mount island'
Silia = sek, 'cut' now Sark, serk, 'sleeveless tunic' the sleeve being the nearby island of Herm, erm, 'sleeve' (The two parts of Sark are joined by a low lying narrow spit)
Andium = ande, 'large' now Jersey, jarth|ey 'earth or land island' being the closest to the mainland (Jersey is the biggest of the islands on the route to the mouth of the Loire)