It is believed that the name "Tokaido" includes the meaning "Umi-no-michi" (literally, "sea road") rather than "Yama-no-michi" (literally, "mountain road," which is the meaning that the name "Tozando" includes) because, in addition to the route from Sagami to Kazusa mentioned above, it also provides a route across the sea at Ise Bay from Mikawa-no-kuni to Ise-no-kuni.
なお、「東海道」の呼称は上記の相模-上総のルートとともに、三河国から伊勢湾を経由して伊勢国に渡る別ルートという海上ルートを含んでいたために、「ヤマノミチ（東山道）」に対する「ウミノミチ」の意味で命名されたと考えられている。