This article presents a brief genealogy and a theory of the ‘improper name’, defined as the adoption of the same pseudonym by organized collectives, affinity groups and individual authors. On the one hand, improper names provide anonymity and a medium for identification and mutual recognition to a subaltern social group. On the other hand, they enable those who do not have a voice of their own to acquire a symbolic power outside the boundaries of an institutional practice. By expressing a multiplicity of pragmatic and semiotic usages, improper names are collective assemblages of enunciation characterized by the proliferation of difference. Drawing from Deleuze and Guattari's distinction between the minor and the major mode, the article suggests that the improper should be thought of as a movement of deterritorialization of the proper. Kripke's anti-descriptivist theory of rigid designation has shown how proper names have the function of fixing a referent in all its possible universes through an initial baptism recognized by a community of speakers. Yet multiple appropriations of the same pseudonym show that proper names may also designate subjects that are not fully individuated. The article concludes by linking the notion of the improper to Gilbert Simondon's theory of subjectification as trans-individuation.