Latin in the traditional language of the Catholic Church ... so it stands to reason that a lot of religious words we use come from Latin. Some examples:

Pagan: From paganus, the Latin word for "peasant," a tiller of the soil. (Peasants, who lived out in the countryside, were among the last classes of people to convert to Christianity.)

Mass: The name is believed to come from the phrase that ended the Latin Mass: Ite, missa est, which means, "Go, you are dismissed."

Profanity: From pro and fanum, which mean "outside the temple," or "unholy."

Fanatic: Also from the Latin word fanum; originally meant "inspired by God."

Infidel: From infidelis, which means "having no faith."

Sacred: From sacer, the Latin word for "set apart." ("Sacrifice" has the same root.)

Crucify: From crux and figo, the Latin words for "cross" and "affix."

Cloister: From claustrum, which means "enclosed space." ("Claustrophobia" has the same root.)

Genuflect: From the Latin words genu, meaning "knee," and flectere, "to bend."

Morals: From mores, the Latin word for "customs."

Nun: From nonna, the word for "child's nurse."

Rosary: From rosarium, which means "rose garden."

Pulpit: From pulpitum, the Latin word for "platform."

Friar: From frater, the Latin word for "brother."