to kowtow (traditional greeting, esp. to a superior, involving kneeling and pressing one's forehead to the ground)

rough or uneven, typically describing the condition of a road or path

to knock against or bump into something, potentially causing damage

(onom.) knocking sound

To kowtow rapidly and repeatedly, typically out of extreme fear or to beg for mercy.

(dialect) knee

to cause something, typically a hard object like a tooth or a fragile item, to break or snap through a collision or impact.

(dialect) to humiliate or ridicule someone

speaking in a broken, hesitant, or stuttering manner, often due to nervousness or a lack of fluency

(coll.) to fight to the death