heart strings

Noun

heartstrings pl (normally plural, singular heartstring)

1. (historical, plural, plural-normally) The tendons or other structures resembling cords once thought to be attached to, or to brace, the heart; especially the aorta, pulmonary artery, and other large arteries connected to them; also, the diaphragm.
   • Harte ſtrynges uenies de cuevr.[1530 July 28 (Gregorian calendar), Iohan Palsgraue [i.e., John Palsgrave], “The Table of Substantyues”, in Lesclarcissement de la langue francoyse⸝ […], [London]: […] [Richard Pynson] fynnysshed by...
2. (broadly, plural, plural-normally) Synonym of chordae tendineae (“the cord-like tendons that connect the papillary muscles to the tricuspid valve and the mitral valve in the heart”).
   • The atrioventricular valves are prevented from turning inside out by strands of connective tissue, which run from their underside to the walls of the ventricle. These are the so-called heartstrings or chordae tendin[e]ae.2002, “Applied Physiology A”, in Beryl Stretch, editor, BTEC National Health Studies, Oxford, Oxfordshire: Heinemann Educational Publishers, →ISBN, page 481

   Synonyms:

   chordae tendineae

3. (figuratively, plural, plural-normally) The source of one's deepest emotions or inner feelings, especially compassion or love.
   • The sad eyes of the orphan tugged at my heartstrings.
4. (archaic, figuratively, plural, plural-normally) The essential or vital part of something; the core, the essence, the heart.
   • And for to ſeeke out gemmes and ſome little ſtones, vve ſtrike pits deep vvithin the ground. Thus vvee plucke the very heart-ſtrings out of her [the Earth], and all to vveare on our finger one gemme or precious ſtone, to fulfill our pleaſure and deſire.1601, C[aius] Plinius Secundus [i.e., Pliny the Elder], “[Book II.] Of Earth and the Nature thereof.”, in Philemon Holland, transl., The Historie of the World. Commonly Called, The Naturall Historie...

   Synonyms:

   bowels, sum, brass tacks, core, crux, essence, gist, drift, guts, gravamen