O.E. flicorian "to flutter, flap quickly and lightly," originally of birds. Onomatopoeic of quick motion. Sense of "shine with a wavering light" is c.1600, but not common till 19c. Related: Flickered; flickering.
"woodpecker," 1808 Amer.Eng., possibly echoic of bird's note, or from white spots on plumage that seem to flicker as it flits from tree to tree.