Extremely surprised, shocked, or overwhelmed to the point of being unable to respond. Completely astonished or amazed.
From the literal sense of being knocked to the floor, this figurative use emerged in American English around the 1930s. The metaphor suggests being so surprised that one is metaphorically knocked down, unable to stand or respond normally.
The evolution from 'floored' meaning literally knocked down to figuratively overwhelmed shows how physical metaphors shape our emotional vocabulary - we describe surprise in terms of physical impact because intense emotions genuinely affect our body's stability and balance. Neuroscience confirms this connection: extreme surprise actually can cause momentary disorientation similar to the physical experience of being knocked over.
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