kaput-

Root for head, yielding Latin caput, Germanic *haubuda (English head), Sanskrit kapucchala-.‍​‌​‍​‍​‌​‌​‍​‌​‍​‌​‌​‍​‌​‍​‌​‍​‌​‌​‍​‍​‍​‌​‍​‌​‌​‌​‍​‍​‌​‍​‍​‌

Discussion

The PIE noun *kaput- (head, top of the body) produced one of the most institutionally consequential ‍​‌​‍​‍​‌​‌​‍​‌​‍​‌​‌​‍​‌​‍​‌​‍​‌​‌​‍​‍​‍​‌​‍​‌​‌​‌​‍​‍​‌​‍​‍​‌word families in the Western vocabulary — a chain of descendants linking the human head to political leadership, financial capital, and legal execution.

Latin caput (head — genitive capitis) is the central reflex and one of the most derivative-rich nouns in the language: capital (pertaining to the head — a capital city is the "head city," capital punishment is punishment "of the head," and capital in the financial sense is the "head" of a sum of money), captain (the head of a group), chapter (caput → capitulum, a division or "little head" of a book), chief (from Old French chef, from Latin caput — the chief is the head), chef (the head of a kitchen — the same word as chief, borrowed at a different period), achieve (OF achever, "to come to the head/end" of something), decapitate (dē-capitāre, "to remove the head"), precipice (prae-cipitium, "headfirst fall"), and recap (to head again, to summarise).

The financial sense of capital deserves emphasis. Latin capitāle ("pertaining to the head") came to mean "the principal sum" — the head of a debt, as opposed to the interest (the body that grows from it). This metaphor of money-as-head shaped the entire vocabulary of capitalism: capital, capitalism, capitalist, capitalise, per capita ("per head," the standard measure of economic output per person).

German Haupt (head — poetic/formal) continues the root through the Germanic branch with regular Grimm's Law shifts: PIE *k > PGmc *h, PIE *p > PGmc *f (with later developments). English head itself is NOT from this root — it comes from PGmc *haubudą, from a different PIE formation. But the Latinate capital family compensates richly for the native word's absence.

Sanskrit kapucchala- (back of the head, hair-knot) may preserve an Indo-Iranian reflex, though the connection is debated.

The root's journey from body part to institution encodes a political philosophy: the leader IS the head, the seat of government IS the capital, the money that drives commerce IS the capital sum. When English speakers talk about human capital, social capital, or political capital, they are using a PIE body-part word to describe abstract value — the head as the measure of all things.

Notes

Pokorny 529. Widely attested nominal form.