English
franken-
Back-formation from Frankenstein.
The story
The prefix references the 1818 novel Frankenstein; or, The Modern Prometheus, in which the mad scientist Victor Frankenstein creates a monster out of various human body parts.
Today it means
prefix Indicating artificiality or a combination of disparate elements, often terrifying or unattractive; often denoting a GMO ("genetically modified organism") product.
Language periods are conventional ranges, not dates for this word.
Etymograph / franken-