The word '都 (tsu),' or '津 (tsu)' are Manyo-kana letters, an archaic form of the Japanese language, which correspond to ancient particle 'tsu' (possessive marker), today's equivalent of '--- no'.
「都・津（つ）」は、上代の格助詞「つ」に当てた万葉仮名で、「～の」の意味になる。