ḱerd-

The root *ḱerd- ("heart") reconstructs a term for the central organ of the body, with reflexes in every major branch of Indo-European. The initial palatal stop *ḱ- is a diagnostic consonant: its treatment distinguishes the centum languages (where it merges with plain *k-) from the satem languages (where it shifts to a sibilant or affricate). Latin cor (genitive cordis) continues the root with regular loss of the initial palatal (merged with plain velar in the centum languages). Derivatives include cordial ("of the heart"), concord ("hearts together"), discord ("hearts apart"), record ("to bring back to heart," i.e., to remember), and courage (through Old French corage, from Latin cor). Greek kardía (καρδία) preserves the dental suffix more transparently. This form is the source of cardiac, endocardium, pericardium, tachycardia, and the clinical vocabulary of cardiology. Sanskrit hr̥d- (genitive hr̥dás) shows the satemisation of *ḱ- > ś- > h- in the Indo-Iranian development. The form hā́rdi ("of the heart") and the compound hr̥daya ("heart") continue the root. The Germanic reflex, with Grimm's Law shifting *k- (from the merged *ḱ-) to *h-, yields Proto-Germanic *hertō, whence Old English heorte (Modern English heart), Old High German herza (Modern German Herz), Old Norse hjarta (Swedish hjärta), and Gothic hairtō. Lithuanian širdìs (with the expected satem reflex *ḱ- > š-) and Old Church Slavonic srŭdĭce (with *ḱ- > s-) continue the Balto-Slavic reflexes. Armenian sirt shows the same satemisation pattern. The phonological history of *ḱerd- thus encapsulates one of the most important classificatory isoglosses in Indo-European: the centum-satem division. The treatment of the initial consonant alone—Latin c-, Greek k-, Germanic h-, Sanskrit h-, Lithuanian š-, Slavic s-—maps the major subgrouping of the family.