In the now extinct Frisian dialect of the island of Wangerooge, the naming verb heit ‘to be called’ had partially grammaticalized into a copular verb ‘to be’ competing, to some extent, with the original copula wízze ‘to be’. In this paper, I discuss the development and the status of the copula heit in some detail and consider what it might tell one about the taxonomy of copular clauses (Higgins 1979). I show that the functional change from naming verb to copula initially occurred in identificational copular clauses. From there heit spread to classifi-cational and specificational copular clauses, but not to predicational ones. This development suggests a principled distinction between predicational copular clauses on the one hand and identificational copular clauses (conceived as comprising classifying, specifying, and equating ones) on the other. This does not imply, however, that heit is an identificational copula or that it selects an identificational small clause. I analyze copular heit used with an identificational small clause as a suppletive allomorph of wízze ‘to be’.*
