TO TURN THE WRONG WAY

The word pervert was first used in English in the late fourteenth century as a verb meaning "alter something from its intended state" (as in pervert the course of justice). The noun form emerged in the 1500s with the definition "one who has been perverted to an immoral set of values". Originally, this didn't have the modern connotation and could refer to people who converted from Christianity, but around the 1850s it came to be associated with sexual deviancy. The word traces to Old French pervertir, which meant "to undo" and further comes from Latin pervertere, meaning "to corrupt" or, more, literally, "to turn the wrong way". Finally, that derives from the prefix per- ("away", from Proto-Indo-European per, "forward") and the root vertere ("to turn", from PIE wer​, also "turn").