The term "Ossho" means the lords of Shoen (manor in medieval Japan) were exempted from and allowed to collect Zatsueki (a kind tax under the Ritsuryo system) (sometimes inclusive of the portion of Kanmotsu (tribute goods -supposed to be paid to Kokuga (provincial government offices) as well as the land of such Shoen.
負所（おっしょ）とは、中世の荘園において、本来は国衙に納めるべき雑役（場合によっては官物の一部を含む）を免除を受け、その分を自己に収めることが出来る荘園領主及びその土地を指す。