The development of double negation in Arabic has attracted increasing attention in recent years. The striking parallels between negation in Berber and North African Arabic invite an explanation in contact terms, and such explanations have indeed been debated. However, in addition to their use in postverbal negation, reflexes of šayʔ have several functions not directly related to negation, notably indefinite quantification and polar question marking. The marking of these functions, too, shows striking Arabic-Berber parallels generally neglected in discussions of the phenomenon. Taking these into account produces a more complete picture of contact influence, and provides clues to the relative chronology of these developments. In some cases, non-Arabic varieties are found to preserve usages obsolete in present-day regional Arabic dialects.