Prose
The word "prose" first appears in English in the 14th century. It is derived from the Old French "prose", which in turn originates in the Latin expression "prosa oratio" (literally, straightforward or direct speech).
Prone position
"Prone" derives from the Latin "pronus": "bent forward, inclined to," from the adverbial form of the prefix "pro-" "forward." Both the original, literal, and the derived figurative sense were used in Latin, but the figurative is older in English.