It's the root of many English words related to the head, like:
* Capital: The head of a country, the most important city.
* Captain: The leader of a group.
* Capitalize: To take advantage of something.
* Capitol: The building where a legislature meets.
* Cephalic: Relating to the head (from the Greek "kephale", also meaning head).
The word "caput" itself is rarely used directly in modern English, but its meaning and influence are seen in many other words.