According to the "Genpei Seisuiki" ("The Rise and Decline of the Minamoto and Taira Clans"), Tadatsuna was derided and nicknamed 'Umano-suke,' (Governor of Noon) because he was Osuke (governor) of Kozuke Province only for the hours of Uma no koku (around noon) between Mi no koku (around 11 am) and Hitsuji no koku (around 1 pm).
巳の刻（午前11時頃）から未の刻（午後1時）までの間の、午の刻のみ上野大介となったことから、「午介」とあだ名されて嘲笑されたと伝えられる（以上、『源平盛衰記』）。