The first uses of "exorbitant" in English was "wandering or deviating from the normal or ordinary course." That sense is now archaic, but it provides a hint as to the origins of "exorbitant": the word derives from Late Latin exorbitans, the present participle of the verb exorbitare, meaning "to deviate."

"Exorbitare" in turn was formed by combining the prefix ex-, meaning "out of," with the noun orbita, meaning "track of a wheel or "rut." ("Orbita" itself traces back to "orbis," the Latin word for "disk" or "hoop.") In the 15th century "exorbitant" came to refer to something which fell outside of the normal or intended scope of the law.

Eventually, it developed an extended sense as a synonym of "excessive."

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