The Latin term immunitas has come a long way from its first registered use in the context of health and disease two thousand years ago. At first, it was employed mainly by non-physicians and understood as a passive exemption from diseases provoked by gods or demons. After the introduction of variolation and Jenner’s inoculation of cowpox in Europe in the eighteenth century, the term began to be used widely by physicians. Soon after came the demonstration of the germ theory of disease and of the first immune mechanisms of defense, which boosted the use of “immunity”, then understood as a protective battle against the germs. In the twentieth century it became clear that immunity could also provoke side effects in the host, and this was followed by the first criticisms of the outdated term, with little success. In next the following decades, the complexity of immunity increased and the military model was substituted by the self/non-self simile and by the neurological one, both complicated by the attribution of new functions to the immune system, which made the term even more obsolete. At present, immunity is mainly regarded as a complex mechanism of integration of microbes into the cell community of the host. From a conceptual point of view, the “immune” system is now considered a “commune” system, but the terminology has not been challenged: does the old term immunitas hamper the understanding of the new idea of immunity? Would it be appropriate to update it? Our main objective will be to answer these questions on the basis of the historical evolution of the term.