"rapid heartbeat," 1868, Modern Latin, coined 1867 by German-born physician Hermann Lebert (1813-1878) from tachy- "swift" + Latinized form of Greek kardia "heart" (from PIE root *kerd- "heart").

"shorthand, stenography, the art of writing in abbreviations," 1640s, from Latinized form of Greek takhygraphia, from takhys "swift" (see tachy-) + -graphia (see -graphy). Related: Tachygraphic; tachygrapher (1849) "stenographer, short-hand taker" (modern or ancient; compare Tironian); tachygraphist (1825).

surveying instrument for rapidly locating position, 1836, from tachy- "swift" + -meter. Related: Tachymetry.

M. GAETANO CAÏRO has invented an instrument, to which he has given the name of Tachymeter ( rapid measurer). Its object is to give the area of plane surfaces bounded by any outline whatever, without the necessity of any arithmetical operation. [Magazine of Popular Science and Journal of the Useful Arts, vol. ii, 1836]

hypothetical faster-than-light particle, 1967, from tachy- "swift" + -on.

"hysterical rapid breathing," 1896, from tachy- "swift" + -pnea, from pnein "to breathe" (see pneuma). Related: Tachypneic.