suru verb (precursor)
lower one's head; cast down one's eyes
Archaic su-verb (precursor to modern suru). Used in classical Japanese to describe lowering one's head or gaze, often in shame or deference. Not used in modern speech; replaced by 俯く (うつむく) or 伏せる (ふせる).
古典では「俯す」と書いて「ふす」と読み、頭を低くする意を表した。
In classical texts, 俯す is read as ふす and means to lower one's head.