blank (adj.) Look up blank at Dictionary.com
early 13c., "white, pale, colorless," from Old French blanc "white, shining," from Frankish *blank "white, gleaming," or some other West 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" (see bleach (v.)).

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.
blank (n.) Look up blank at Dictionary.com
late 14c. as the name of a small French coin; 1550s as "white space in the center of a target," from the same source as blank (adj.). Meaning "empty space" (in a document, etc.) is from c.1570. Meaning "losing lottery ticket" (1560s) is behind the expression draw a blank. The word has been "for decorum's sake, substituted for a word of execration" [OED] from 1854. From 1896 as short for blank cartridge (itself from 1826).
blank (v.) Look up blank at Dictionary.com
1540s, "to nonplus, disconcert, shut up;" 1560s, "to frustrate," from blank (adj.). Sports sense of "defeat (another team) without allowing a score" is from 1870. Meaning "to become blank or empty" is from 1955. Related: Blanked; blanking.