Mytho-history referred to history contained in mythology, specifically, true historical recollections that were mixed with certain mythological elements.
The hunter Darmok on Shantil III was considered to be a mytho-historical figure.
While investigating the Tamarian language, Lieutenant Commander Data was able to ascertain that "the Tamarian ego structure does not seem to allow what we normally think of as self-identity. Their ability to abstract is highly unusual. They seem to communicate through narrative imagery by reference to the individuals and places which appear in their mytho-historical accounts." (TNG: "Darmok")