In the ancient times, the concept of hyakusho was all classes with surnames that were classified as "Ryo" (law-abiding people) in a family register under the Ritsuryo system, i.e., nobles, government officials, citizens, and zoshikinin (lower-level functionaries in the provincial government), excluding emperors, humble or lowly people without a surname who were classified as "Sen" such as slaves, and Emishi (northerners) who were classified as social outcasts.
古代においては律令制のもとで戸籍に"良"と分類された有姓階層全体、すなわち貴族、官人、公民、雑色人が百姓であり、天皇、及び"賎"とされた無姓の奴婢などの賎民、及び化外の民とされた蝦夷などを除外した概念であった。