In this paper I will analyze and trace samples of a tribal dialect that thrived in medieval Islam and has survived into the modern period. It is a mixed language or para-language that takes the form of embedding a substitutive vocabulary into the grammatical structure of other languages and it has historically been spoken within communities of peripatetics and commercial nomads, or Gypsy 1 groups. In 10th-century Arabic sources produced in Būyid Iraq and Iran, non-speakers named this language lughat al-mukaddīn (the language of the beggars), another demonstration of an outsider’s perspective. However, speakers of this language called it lughat Banī Sāsān (the language of the Sāsān clan) or lughat al-shaykh Sāsān (the language of the Master Sāsān). The language, in name and application, was not identified with a territory or an ethnicity, but rather with a peripatetic tribal group, the Banū Sāsān, whose members worked as beggars and entertainers. As early as the 13th century, speakers of this language referred to it as al-sīn and non-speakers named it lughat/lisān al-ghurabāʾ (the language of the Gypsies). Between the 13th and 15th centuries, Arabic and Persian writers composed texts explaining various Sāsānī words to their Arabic and Persian-speaking audiences. Texts also survive from this period with snippets of sīn prose and poetry.