The stethoscope and its name were invented on the same day, by the same man, in a single flash of embarrassed ingenuity. In 1816, the French physician René Théophile Hyacinthe Laennec was examining a young woman at the Necker Hospital in Paris. The standard method of listening to the heart was immediate auscultation — placing the ear directly against the patient's chest. Laennec found this impractical and immodest in the circumstances. He recalled that sound traveled well through solid objects, rolled a quire of paper into a tight cylinder, placed one end against the woman's chest and the other against his ear — and heard the heartbeat more clearly than he had ever heard it by any other method. He had invented the stethoscope, though it took him three years to name it.
In 1819, Laennec published 'De l'Auscultation Médiate' (On Mediate Auscultation), presenting his instrument and his findings. He coined the word 'stéthoscope' from Greek 'stēthos' (στῆθος, chest) and 'skopein' (σκοπεῖν, to look at, to examine). The Greek suffix '-scope' was already well established in scientific nomenclature: the telescope (far-looker) had been named in the early seventeenth century, and the microscope shortly after. Laennec's coinage was immediately intelligible to any educated European: this was an instrument for examining the chest.
The Greek root 'skopein' descends from PIE *spek- (to observe, to look), one of the most productive roots in the Indo-European family. Latin 'specere' (to look) from the same root gave English 'species,' 'specimen,' 'spectacle,' 'inspect,' 'expect,' and 'suspect.' The English word 'bishop' traces back through Old English to Latin 'episcopus,' from Greek 'episkopos' (overseer) — 'epi-' (over) + 'skopein' (to look), the same root as '-scope.' A bishop is etymologically an overseer; a stethoscope is an overseer of the chest.
The Greek 'stēthos' (chest) is of less certain PIE ancestry, though it likely relates to roots meaning standing firm or the standing part of the body (the torso). In Greek medical literature 'stēthos' referred to the front of the chest and sometimes to the breast more generally. Laennec's instrument was initially a monaural device — a wooden tube applied to one ear — and evolved through the nineteenth century into the binaural instrument (two earpieces, one chest piece) that became the universal symbol of the medical profession.
Laennec himself died of tuberculosis in 1826, a disease he had spent years studying through his stethoscope. The instrument he invented to listen to diseased lungs eventually helped diagnose the consumption that killed him. He was thirty-nine years old. The stethoscope remains the most widely recognized icon of medicine, and the word Laennec coined in 1819 remains unchanged nearly two centuries later.