Al-nisab allatī ʿalā khilāf ẓāhirihā
Affiliations whose real cause differs from their apparent implication.
A designation such as al-Ḥadhdhāʾ might suggest a shoemaking occupation, but a particular bearer need not have worked in that trade. Sulaymān al-Taymī was associated with Banū Taym through residence among them rather than necessarily through descent from that tribe.
A nisba is therefore not conclusive proof of lineage, trade, or birthplace. Establishing its actual cause removes errors in interpreting narrators’ social and geographic identities.