early 13c., "white, pale, colorless," from Old French blanc "white, shining," from Frankish *blank "white, gleaming," or some other Germanic source (compare Old Norse blakkr, Old English blanca "white horse;" Old High German blanc, blanch; German blank "shining, bright"), from Proto-Germanic *blangkaz "to shine, dazzle," extended form of PIE root *bhel- (1) "to shine, flash, burn," also "shining white."
Meaning "having empty spaces" evolved c. 1400. Sense of "void of expression" (a blank look) is from 1550s. Spanish blanco, Italian bianco are said to be from Germanic. Related: Blankly, blankness.
c. 1300, "coarse white woolen stuff," also "a large oblong piece of woolen cloth used for warmth as a bed-covering" (also as a cover for horses), from Old French blanchet "light wool or flannel cloth; an article made of this material," diminutive of blanc "white" (see blank (adj.)), which had a secondary sense of "a white cloth."
As an adjective, "providing for a number of contingencies," 1886 (blanket-clause in a contract). Wet blanket (1830) is from the notion of a person who throws a damper on social situations in the way a wet blanket smothers a fire. In U.S. history, a blanket Indian (1859) was one using the traditional garment instead of wearing Western dress.
Only 26,000 blanket Indians are left in the United States. [Atlantic Monthly, March 1906]
1570s, in gunnery, "having a horizontal direction," said to be from point (v.) + blank (n.), here meaning the white center of a target. The notion would be of standing close enough to aim (point) at the blank without allowance for curve, windage, or gravity.
But early references make no mention of a white target, and the phrase is possibly from a simplification of the French phrase de pointe en blanc, used in French gunnery in reference to firing a piece on the level into open space to test how far it will carry. In that case the blank represents "empty space" or perhaps the "zero point" of elevation. The whole phrase might be a French loan-translation from Italian.
From 1590s as an adjective in English. The transferred meaning "direct, blunt, straight, without circumlocution" is from 1650s.