c.1200, "moral stain," probably from O.E. splott "a spot, blot, patch (of land)" infl. by M.Du. spotte "spot, speck." Other cognates are E.Fris. spot "speck," N.Fris. spot "speck, piece of ground," O.N. spotti "small piece." It is likely that some of these are borrowed, but the exact evolution now is impossible to trace. Meaning "speck, stain" is from c.1340. The sense of "particular place" is from c.1300. Meaning "short interval in a broadcast for an advertisement or announcement" is from 1923. Proceeded by a number (e.g. five-spot) it originally was a term for "prison sentence" of that many years (1901, Amer.Eng. slang). To put (someone) on the spot "place in a difficult situation" is from 1928. Colloquial phrase to hit the spot "satisfy, be what is required" is from 1868. Spot check first attested 1933. Spot on "completely, accurately" is attested from 1920.
early 15c., "to stain, sully, tarnish" from spot (n.). Sense of "to stain with spots" is attested from mid-15c. Meaning "to see and recognize," is from 1718, originally colloquial and applied to a criminal or suspected person; the general sense is from 1860.