Aracoeli is the original Latin spelling of Araceli. I think in church Latin it is "air-ah-CHAY-lee", with the middle syllable rhyming with the start of words like "chase" or "chain".
The name means "altar of heaven" in Latin. It originally referred to a site on the Capitoline hill in Rome where there was a temple to the god Jupiter. After Christianity triumphed, the temple was replaced by a church dedicated to the Virgin Mary, but the name "Aracoeli" was retained. Aracoeli and Araceli became female given names as an example of devotion to the Virgin Mary, just as other place names with shrines dedicated to her, such as Pilar, Guadalupe, and Montserrat, also became female given names.