flicker v.

Middle English flikeren, from Old English flicorian "to flutter, flap quickly and lightly, move the wings," originally of birds. Onomatopoeic and suggestive of quick motion. With Germanic verbal suffix indicating repeated or diminutive action (see -er (4)). The sense of "shine with a wavering light" is c. 1600 but was not common before 19c. Related: Flickered; flickering.

1849, "wavering, unsteady light or flame;" 1857 as "a flickering," from flicker (v.).

type of North American woodpecker, 1808, American English, said to be echoic of bird's note, or from black spots on plumage of the underparts that seem to flicker as it flits from tree to tree.