"from a higher to a lower place, state, or condition," late 12c., from down (adv.) + -ward. As a preposition, "down," by late 14c. As an adjective, "moving or tending from a higher to a lwer place, state, or condition," from 1550s. As an adverb Old English had aduneweard. Downwards (c. 1200), with adverbial genitive, had a parallel in Old English ofduneweardes.
"short, quick, forward and downward motion of the head," voluntary or not, 1530s, from nod (v.).
1710, "a downward movement," from down (adv.). Football sense of "an attempt to advance the ball" is by 1882.
1550s, "cause to turn aside" (transitive), from Latin deflectere "to bend (something) aside or downward," from de "away" (see de-) + flectere "to bend," which is of uncertain origin. The intransitive sense of "to turn away or aside" is from 1610s. Related: Deflected; deflecting.