1550s, "occurring or acting by turns, one after the other," present-participle adjective from alternate (v.). Electrical alternating current is recorded from 1839, an electrical current which flows alternately in opposite directions without interruption.

of persons, "weakened and disordered or agitated by shocks," 1640s, past-participle adjective from shake (v.). By 1725 as "put into quick or vigorous alternating motion."

also checkerboard, "board divided into 64 small squares of alternating color," 1779, from checker (n.1) + board (n.1).

"pattern of squares in alternating colors," c. 1400, short for checker (n.1). As a fabric having such a pattern from 1610s.

"having the tail ringed with alternating colors," 1725 in ornithology, by 1729 in zoology, from ring (n.1) + tail (n.).

"violent muscular spasms, rapidly alternating contraction and relaxation of a muscle," 1817, from Modern Latin, from Greek klonos "turmoil, any violent motion; confusion, tumult, press of battle," a word of uncertain origin. Related: Clonicity.

early 15c., "rapid repetition of words," from a rhyming reduplication of patter (v.2). As "alternating light beating sounds," 1670s, from patter (v.1). As a verb in this sense by 1708. Compare pit-a-pat.