Old English heorte "heart; breast, soul, spirit, will, desire; courage; mind, intellect," from Proto-Germanic *khertan- (cf. Old Saxon herta, Old Frisian herte, Old Norse hjarta, Dutch hart, Old High German herza, German Herz, Gothic hairto), from PIE *kerd- "heart" (cf. Greek kardia, Latin cor, Old Irish cride, Welsh craidd, Hittite kir, Lithuanian širdis, Russian serdce "heart," Breton kreiz "middle," Old Church Slavonic sreda "middle").
Spelling with -ea- is c.1500, reflecting what then was a long vowel, and remained when pronunciation shifted. Most of the figurative senses were present in Old English, including "intellect, memory," now only in by heart. Heart attack attested from 1875; heart disease is from 1864. The card game hearts is so called from 1886.
The chambered, muscular organ in vertebrates that pumps blood received from the veins into the arteries, thereby maintaining the flow of blood through the entire circulatory system.
A similarly functioning structure in invertebrates.
According to the Bible, the heart is the centre not only of spiritual activity, but of all the operations of human life. "Heart" and "soul" are often used interchangeably (Deut. 6:5; 26:16; comp. Matt. 22:37; Mark 12:30, 33), but this is not generally the case. The heart is the "home of the personal life," and hence a man is designated, according to his heart, wise (1 Kings 3:12, etc.), pure (Ps. 24:4; Matt. 5:8, etc.), upright and righteous (Gen. 20:5, 6; Ps. 11:2; 78:72), pious and good (Luke 8:15), etc. In these and such passages the word "soul" could not be substituted for "heart." The heart is also the seat of the conscience (Rom. 2:15). It is naturally wicked (Gen. 8:21), and hence it contaminates the whole life and character (Matt. 12:34; 15:18; comp. Eccl. 8:11; Ps. 73:7). Hence the heart must be changed, regenerated (Ezek. 36:26; 11:19; Ps. 51:10-14), before a man can willingly obey God. The process of salvation begins in the heart by the believing reception of the testimony of God, while the rejection of that testimony hardens the heart (Ps. 95:8; Prov. 28:14; 2 Chr. 36:13). "Hardness of heart evidences itself by light views of sin; partial acknowledgment and confession of it; pride and conceit; ingratitude; unconcern about the word and ordinances of God; inattention to divine providences; stifling convictions of conscience; shunning reproof; presumption, and general ignorance of divine things."