floor

Reader's Digest 10月号の記事RAISING OBAMAから引用します。
Bryant remembered, almost four decades later, "I was floored that she'd bring a half-black child to Indonesia, knowing the disrespect they had for blacks. I remember thinking. They're more racist than the US."
床以外の "floor" としては前に発言権の意味を取り上げましたが上の引用文に出てきた動詞の "floor" にはまた別の意味があるようです。
・Collins Dictionary: (informal) to disconcert, confound, or defeat ⇒ to be floored by a problem
・Vocabulary.com: surprise greatly; knock someone's socks off: “I was floored when I heard that I was promoted”
・Macmillan Dictionary: to make someone feel so surprised and confused that they cannot react: The question floored him completely.
何故この様な意味を持つ様になったのかは " Sense of "puzzle, confound" is 1830, from notion of "knock down to the floor" (1640s). " とOnline Etymologyに書かれていました。