Yarmaqs were silvercoins minted in the Khazar Khaganate and other Turkic polities in medieval Eurasia. The name is similar to Mongolian language word "yaarmag" meaning "market," especially outdoor ones that sell wide variety of goods.
Roman K. Kovalev. "What Does Historical Numismatics Suggest About the Monetary History of Khazaria in the Ninth Century? – Question Revisited." Archivum Eurasiae Medii Aevi 13 (2004): 97–129.
Roman K. Kovalev. "Creating Khazar Identity through Coins: The Special Issue Dirhams of 837/8." East Central and Eastern Europe in the Early Middle Ages, ed. Florin Curta, pp. 220–253. Ann Arbor, MI: University of Michigan Press, 2005.