Another one without a specific date attached to it. Heart comes from the Old English heorte, which could mean heart, breast, soul, mind, or even desire. Heorte comes from the Proto Germanic khertan- (yes, a K!) and before that, the Proto Indo European kerd-, meaning heart. Interesting factoid of the day: the reason heart has an “ea” spelling is because it used to have a long vowel sound, meaning “ee” instead of “ah”. It’s one of the many cases in etymology where you’ll find pronunciation shifted but spelling didn’t.
Tony Jebson’s page on the Origins of Old English
University of Texas at Austin Linguistic Research Center