also wiretapping, "surreptitiously obtaining information by connecting wires to telegraph (later telephone) lines and establishing an intermediate station between two legitimate ones," 1878, from wire (n.) + agent noun from tap (v.2). Earliest references often are to activity during the American Civil War, but the phrase does not seem to have been used at that time. Related: Wire-tap; wire-tapper.

"strike lightly," c. 1200, from Old French taper "tap, rap, strike" (12c.), from a Gallo-Roman or Germanic source ultimately imitative of the sound of rapping. Meaning "to designate for some duty or for membership" is recorded from 1952, from notion of a tap on the shoulder. Related: Tapped; tapping.

1620s, "an embrace about the neck then the tapping of a sword on the shoulders to confer knighthood," from French accolade "an embrace, a kiss" (16c.), from Provençal acolada or Italian accollata, ultimately from noun use of a fem. past participle of Vulgar Latin *accollare "to embrace around the neck," from Latin ad "to" (see ad-) + collum "neck" (compare collar (n.)), from PIE root *kwel- (1) "revolve, move round." Also see -ade.

The extended meaning "praise, award" is by 1851. The earlier form of the word in English was accoll (mid-14c.), from Old French acolee "an embrace, kiss, especially that given to a new-made knight," a noun use of the past participle of the verb acoler. The French noun in the 16c. was altered to accolade, with the foreign suffix, and English followed suit.

early 15c., percussioun, "a striking, a blow; internal injury, contusion," from Latin percussionem (nominative percussio) "a beating, striking; a beat as a measure of time," noun of action from past participle stem of percutere "to strike hard, beat, smite; strike through and through," from per "through" (from PIE root *per- (1) "forward," hence "through") + quatere "to strike, shake" (see quash).

In reference to musical instruments sounded by a stroke or blow, attested by 1776 (instrument of percussion). In medical diagnosis, "a method of striking or tapping the surface of the body to determine the condition of the organs in the region struck," by 1781.

The art of percussion, besides, although very simple in appearance, requires long practice, and a dexterity which few men can acquire. The slightest difference in the angle under which the fingers strike the thorax, may lead one to suspect a difference of sound which in reality does not exist. ["Laennec's New System of Diagnosis," in Quarterly Journal of Foreign Medicine and Surgery, November 1819]