Is it ensure, insure, or assure?
c.1300, "ash, cinders; dust of the earth;" early 14c., "pulverized substance;" mid-14c., "medicinal powder;" late 14c. as "gunpowder," from Old French poudre "dust, powder; ashes; powdered substance" (13c.), earlier pouldre (11c.), from Latin pulverem (nominative pulvis) "dust" (see pollen). Specialized sense "gunpowder" is from late 14c. In the sense "powdered cosmetic," it is recorded from 1570s.
In figurative sense, powder keg is first attested 1855. Powder room, euphemistic for "women's lavatory," is attested from 1936. Earlier it meant "place where gunpowder is stored on a warship" (1620s). Powder horn attested by 1530s. Powder puff first recorded 1704; as a symbol of femaleness or effeminacy, in use from at least 1930s.
Phrase take a powder "scram, vanish," is from 1920; it was a common phrase as a doctor's instruction, so perhaps from the notion of taking a laxative medicine or a sleeping powder, with the result that one has to leave in a hurry (or, on another guess, from a magician's magical powder, which made things disappear). Powder blue (1650s) was smelt used in laundering; as a color name from 1894.
c.1300, "to put powder on;" late 14c., "to make into powder," from Old French poudrer "to pound, crush to powder; strew, scatter," from poudre (see powder (n.)). Related: Powdered; powdering.
powder pow·der (pou'dər)
A dry mass of pulverized or finely dispersed solid particles.
Any of various medicinal or cosmetic preparations in the form of powder.
A single dose of a powdered drug.
[sense of running away probably fr similar dust fr the notion of raising dust as one runs; perhaps, in view of take a powder and run-out powder, the asi notion is reinforced by that of taking a medicinal powder, esp a laxative, so that one has to leave in a hurry, or perhaps a magical powder that would cause one to disappear]