Kelly/Kelley is an old Gaelic name originating from the church having to do, somehow, with the church and/or the monestary. Its original meaning has to do with some "position, job or task" that has to do with church related practice, ritual or business.
― Anonymous User 2/16/2008
2
It is possible that the English "Kelly" represents a shift in the pronunciation from "kali," the feminine form of the Ancient Greek word "kalos," (m.) meaning "beautiful." This same root is found in the feminine "Kallista," or "Callista," the superlative of the word meaning, "most beautiful," and alternatively "very beautiful," or "exceedingly beautiful."