It's English in reverse. Listen.
4 seconds sound clip from the The Exorcist movie soundboard.
You can hear this line at 01:35:50 in the Blu-ray version of the movie.
Quote context
[...]
- She pushed him out her window.
- It's a language, all right. It's English.
- It's English in reverse. Listen.
- Fear the priest. Fear the priest.
- Merrin!
[...]