From rarum to rarissimum: An unexpected zero person marker

This article addresses the problem of crosslinguistic rarity by mapping the types of diachronic factors that contribute to the rarity of a particular feature. It is proposed that a number of different diachronic factors may play a role, such as the rarity of source constructions, the rarity of particular types of change, the number of stages necessary for a particular feature to develop, and the number of pathways that can lead to a particular feature. This article looks at a rarissimum of person marking, namely, a zero-marked feminine 2nd singular person index in the Sahidic dialect of Coptic (Afroasiatic; Egypt). It is argued that such markers are rare because they presuppose rare input structures, and most processes of change would lead away from - rather than to - zero-marked 2sg. Furthermore, this study identifies a diachronic process in which a part of a morpheme is reinterpreted as a segmentable morpheme (in this case, a person index), thereby leading to the loss of a zero person marker. This is the converse of the well-known "Watkins' Law", in which a segmentable person marker is reinterpreted as part of a base.