I don't have a definite answer for you. The Mimic might be based on a combination of folklore, myths, or the author's imagination. It's hard to pin down a specific source.
Well, 'the mimic ghost story' could potentially revolve around a haunted place where a ghost has the ability to mimic. Maybe it mimics the appearance of someone you know to lure you into a dangerous situation. It could also be a story of a vengeful spirit that uses mimicry as a form of torment for the living.
Once upon a time, there was a mimic spirit in a forest. It could take on the forms of various things it saw. One day, it saw a beautiful woman. It was so fascinated that it decided to transform into a woman. It mimicked her every feature, from her long flowing hair to her graceful walk. And so, it became a woman - like figure, living among the trees, sometimes scaring the local villagers who thought it was a real woman but with an otherworldly air.