c. 1400, transitive, "to make white, cause to turn pale," from Old French blanchir "to whiten, wash," from blanc "white" (11c.; see blank (adj.)). In early use also "to whitewash" a building, "to remove the hull of (almonds, etc.) by soaking." Intransitive sense of "to turn white" is from 1768. Related: Blanched; blanching.
"to start back, shrink, turn aside," 1570s, variant of blench (q.v.). Related: Blanched; blanching.