A sudarium (Latin) was a "sweat cloth", used for wiping the face clean. Small cloths of various sorts, for which sudarium is a general term, played a role in Ancient Roman formal manners and court ceremonial, and many such uses transferred to Christian liturgical usage and art.

SUDARIUM
The Sudarium of Oviedo and its Relationship with the Shroud of Turin
The Sudarium from Bagau-Reason for Several Historical Considerations and Interpretations
Turin Shroud and Sudarium of Oviedo: analysis and comparison by computer science methods
New coincidence between Shroud of Turin and Sudarium of Oviedo
New coincidence between Shroud of Turin and Sudarium of Oviedo
Commonalities between the Shroud of Turin and the Sudarium of Oviedo
Commonalities between the Shroud of Turin and the Sudarium of Oviedo
The question of pollen grains on the Shroud of Turin and the Sudarium of Oviedo
Icons, Science, and Faith: Comparative Examination of the Shroud of Turin and the Sudarium of Oviedo