h₃orbʰ-it-
“circular path, track”orbit, orbital
Extended form of *h₃orbʰ- giving Latin orbita, English orbit, orbital.
Discussion
The PIE form *h₃orbʰ-it- (circular path, track, beaten way) may derive from a root *h₃erbʰ- (to turn, to change), though the exact morphological analysis is debated. The form produced Latin orbita (wheel-track, beaten path, circular course) and the broader noun orbis (circle, ring, disk, world).
Latin orbis (circle, ring — and by extension the world, conceived as a disk) gave English: orbit (the circular path of a celestial body — Kepler showed these were elliptical, not circular, but the word persisted), orbital (pertaining to an orbit — used in astronomy, anatomy for the eye socket, and chemistry for electron paths), and orb (a sphere, especially a ceremonial globe carried by monarchs). The phrase orbis terrarum ("circle of lands" — the entire known world) was the Roman equivalent of "the globe."
The specific derivative orbita (a wheel-rut, a track left by a turning wheel) gave English orbit through the medieval astronomical use: the planet's path was conceived as a groove or rut in the celestial sphere through which it rolled. The image of cosmic mechanics as wheel-tracks in the sky is quintessentially ancient — and the word orbit preserves it.
The derivative exorbitant (ex-orbitāre, "to go out of the track" — to deviate from the normal circular path) acquired its modern meaning of "excessive" through the idea that exceeding the normal track implies excess. An exorbitant price is one that has left the track of reason.
The word suburb (sub-urbem, "below/near the city" — from urbs, which some connect to orbis through the concept of the walled enclosure) may be distantly related, though this etymology is debated.