Unscientific data usually which is based on the personal experience of the ones narrating it. Usually, investigations where facts and scientific clues are not present, this type of evidence are used where witnesses have an important role as compared to the other evidence present (if present, as it is lacking in such cases).
Diagrams
Originated from/Coined by
Further Reading/ References
https://www.merriam-webster.com/dictionary/anecdotal