Antigrammaticalization

Antigrammaticalization is a morphosyntactic change that is the opposite of grammaticalization in that it "leads from the endpoint to the starting point of a potential grammaticalization and also shows the same intermediate stages" (Haspelmath 2004:27-28).

Example
In Irish, the first person plural subject suffix -muid was antigrammaticalized to become the independent personal pronoun muid.

Comment
Antigrammaticalization is a special case of degrammaticalization. Originally, degrammaticalization referred exclusively to antigrammaticalization, but especially in the 1990s the use of its term has been extended so much that a new term is useful.

Origin
The term was coined by Haspelmath (2004:27), first presented at the conference New Reflections of Grammaticalization 2 in Amsterdam (February 2002).

Reference

 * Haspelmath, Martin. 2004. On directionality in language change with particular reference to grammaticalization. In: Olga Fischer, Muriel Norde and Harry Perridon (eds). Up and down the cline: The nature of grammaticalization. (Typological Studies in Language, 59.) Amsterdam: Benjamins, 17-44.

Other languages
German Antigrammatikalisierung