If one googles, one finds that Oxford Languages (ex 'Lexico' etc) claims that the etymology of dupe is that the word is based on the old French word for a type of bird thought to be unintelligent:
- date 17th century: from dialect French dupe [‘hoopoe’], from the bird's supposedly stupid appearance.
But it seems to me the word might be related instead to the word "duplicate" since many sleight of hand tricks or con artist scams rely on the replacement of the actual object with a duplicate.
I find the bird explanation fairly contrived whereas the derivation from duplicate sounds closer. How can I pursue this further?