ḱred-
“heart, core belief”creed, credit, credible, incredible
Root yielding Latin crēdere (from *ḱred-dʰeh₁-), English creed, credit, credible, incredible.
Discussion
The PIE compound *ḱred- represents one of the most elegant semantic constructions in the reconstructed vocabulary: it combines *ḱerd- (heart) with *dʰeh₁- (to place, to put), yielding the literal meaning "to place one's heart" — to invest emotional conviction, to trust, to believe. The compound is not a metaphor imported from a daughter language but a PIE-level formation, confirmed by the independent survival of the same compound in Latin and Sanskrit with the same meaning.
Latin crēdere (to believe, to trust, to entrust) continues *ḱred-dʰeh₁- directly: crē- from *ḱred- (heart-) and -dere from *dʰeh₁- (to place). The derivatives are among the most consequential in institutional English: creed (a statement of belief, from Latin crēdō, "I believe" — the first word of the Christian Nicene Creed), credit (belief in someone's ability to repay — financial trust), credible (worthy of belief), incredible (too extraordinary for belief), credulous (too willing to believe), credentials (documents that entitle belief), and accredit (to grant official belief/recognition).
The financial sense of credit deserves emphasis: to give someone credit is, etymologically, to place your heart with them — to trust them with your resources. The entire modern credit system — credit cards, credit scores, credit ratings — rests on a PIE metaphor of the heart as the organ of trust. When a bank extends credit, it is performing an act that PIE speakers would have recognised: placing its heart (its confidence, its resources) in the borrower.
Sanskrit śrad-dhā- (faith, trust, confidence) preserves the compound independently with identical structure: śrad- from *ḱred- (heart) and -dhā- from *dʰeh₁- (to place). The Vedic śraddhā is a central religious concept — the faith that motivates sacrifice, the trust placed in the gods and in the ritual. The structural identity of Latin crēdere and Sanskrit śrad-dhā- — same compound, same meaning, same morphology — is one of the celebrated proofs of the comparative method.
Old Irish cretid (he believes) confirms the Celtic reflex of the same compound. The pan-IE distribution — Italic, Indo-Iranian, Celtic — with identical semantics confirms that the metaphor of "placing the heart" was already established in PIE, not an independent development in any single branch. The PIE speakers who coined this compound understood what neuroscience is only now confirming: that belief is not a purely cognitive act but an emotional investment, a commitment of the heart.