Jahālah (unknown status) means that the evidence does not sufficiently establish a narrator's probity and precision. The fact that someone's name appears in a chain does not itself constitute endorsement.
«بِأَنْ لَا يُعْرَفَ فِيهِ تَعْدِيلٌ وَلَا تَجْرِيحٌ مُعَيَّنٌ»
That is, no specific accreditation or criticism is known concerning the person.
Illustration: A name occurs in a single chain, but biographical evidence about the person and the assessments of specialists are insufficient. “No criticism has been found” is not the same as “probity has been established.” Detailed types of unknown narrators belong to later discussion.