"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."
Entries linking to tachycardia
tachy-
word-forming element meaning "rapid, swift, fast," from Latinized combining form of Greek takhys "swift, rapid, hasty," related to takhos "speed, swiftness," of uncertain origin.
*kerd-
Proto-Indo-European root meaning "heart."
It forms all or part of: accord; cardiac; cardio-; concord; core; cordial; courage; credence; credible; credit; credo; credulous; creed; discord; grant; heart; incroyable; megalocardia; miscreant; myocardium; pericarditis; pericardium; quarry (n.1) "what is hunted;" record; recreant; tachycardia.
It is the hypothetical source of/evidence for its existence is provided by: Greek kardia, Latin cor, Armenian sirt, Old Irish cride, Welsh craidd, Hittite kir, Lithuanian širdis, Russian serdce, Old English heorte, German Herz, Gothic hairto, "heart;" Breton kreiz "middle;" Old Church Slavonic sreda "middle."