Vodun is a Fon word, and it is the clearest case in the atlas of a single term travelling from one West African language into the vocabulary of three continents. It names a deity or a spiritual power, and it entered Haitian Creole, Brazilian Portuguese, French and English, acquiring in the last of these a set of sensational associations that have nothing to do with its meaning in Fon.
Inside Benin the language carries a religious register that is not open to everyone. The vodun have praise names and salutations that are learned rather than looked up; the songs of the convent belong to the period of seclusion in which initiates are taught them; and the verses attached to the Fa divination signs are a memorised corpus held by diviners. Public festivals are attended by anyone. The initiatory material is not public, and the atlas records that it exists and is restricted rather than setting it out.
What crossed the Atlantic crossed as language. Captives shipped through Ouidah and from Allada carried Fon names for deities, and those names are still spoken in the Americas. The Rada rite of Haitian Vodou takes its name from Allada. Legba, Damballa and other Haitian lwa carry Fon or Gbe names, and the liturgical songs of Haitian, Cuban and Brazilian houses preserve phrases whose speakers no longer parse them as sentences but transmit them exactly, which is why they can still be recognised on the African side.