It is one of the typical jokes with last names, very common in these stories. In this case, it is funny that an Italian singer was called “Potasman”. Other examples: the English tailor’s shop called “Rabuffi” or the Basque “Speciale”. (Mentioned in Bustos Domecq story.)
Index: La fiesta del monstruo, Nuevos cuentos de Bustos Domecq, OCC,Obras completas en colaboración. Buenos Aires: Emecé, 1979. 397.