1. to stand firm
2. to be unprepared
- and why it would have evolved this way.
From Dictionary.com
From Online Etymology Dictionaryflat-foot·ed (fltftd)
adj.
Of or afflicted with flatfoot.
Steady on the feet.
Informal. Without reservation; forthright: a flat-footed refusal.
Unable to react quickly; unprepared: The new product caught their competitors flat-footed.
And from another webpageFlat-footed "unprepared" is 1912 U.S. baseball slang, on notion of "not on one's toes; earlier it meant "straightforwardly" (1828), from notion of "standing firmly."
flat-footed
A player who is stationary when the opposition is moving towards him at a rapid rate is said to be flat footed.
Eg: "Walter Little was unable to keep up as he was caught flat-footed from the start."