Kowtow, which is borrowed from kau tau in Cantonese, is the act of deep respect shown by prostration, that is, kneeling and bowing so low as to have one's head

Kowtow, which is borrowed from kau tau in Cantonese, is the act of deep respect shown by prostration, that is, kneeling and bowing so low as to have one's head touching the ground. In Sinospheric culture, the kowtow is the highest sign of reverence. -wiki