Taboo refers to "a proscription of behaviour for a specifiable community of one or more persons, at a specifiable time, in specifiable contexts" (Allan & Burridge, Forbidden Words: Taboo and the Censoring of Language (Cambridge, 2006), 11). Avoidance of taboo words, expressions believed to be harmful for the speaker or hearers, is a universal phenomenon of language behavior. With regard to medieval Muslim society, it is important to note that taboos did not necessarily overlap with Islamic legal prohibitions, but were often socially-disapproved practices. Hence, if not leading to legal sanction, transgressing a taboo in act or word would lead to social sanction. Words tabooed are usually related to sex, bodily functions and effluvia, sickness and death, and normative Arabic--as other languages--renders them indirectly by means of euphemisms (kinayat). The primary focus of this paper is two medieval Arabic works on euphemisms: the first, the earliest of its kind, was composed by Abu Mansur al-Tha'alibi (350-429/961-1038) and titled Kitab al-kinaya wa-l-ta'rid; the second, relying heavily on al-Tha'alibi's work (without acknowledgment) is Ahmad al-Jurjani's (d. 482/1089) Kinayat al-udaba` wa-isharat al-bulagha`. Topically arranged, Kitab al-kinaya and Kinayat al-udaba` offer numerous euphemistic expressions for the use of any civilized person. Albeit lacking analytic approach, through the abundant euphemisms presented to the reader, these two works reflect well the conventions of censorship and purification of language in society. Approaching the evidence from a sociolinguistic point of view, I map the taboos in medieval Arabic-speaking society as appearing in these sources (and a few others); discuss the explicit and implicit reasons for tabooing certain language behaviors; and outline the linguistic characteristics of the euphemisms produced. I have found that already in the 4th/10th century the short-life of euphemisms due to contamination by the taboo topic and replacement by other expressions has been astutely observed. With regard to the reasons for censuring language, the weight of fear of metaphysical harm befalling the speaker or audience was considerable. This is in contrast to contemporary Western society, in which politeness and face are the main reasons for using euphemisms (see Allan & Burridge, Forbidden Words, 238). Lastly, in creating euphemisms, figurative language sparked by conceptions about the denotata (e.g., menstrual blood, genitals, and feces) was preferred over formal changes in the tabooed expressions (by remodeling or clipping of taboo words).