The purpose of this lexicological study is to present a typology of patients’ euphemizing lay denominations of medical terms illustrated by examples in English and French. Various textbooks and lexicons dealing with English and French for medical purposes served as corpora. The euphemisms were classified according to the three semantic processes by means of which they were created: widening (Eng. down below for “genitals” and Fr. poitrine [lit. ‘chest’] for “breast”), reduction (Eng. miss* for “miscarriage” and Fr. MST [lit. ‘STD’] for “sexually-transmitted disease”), and analogy (Eng. engine for “heart” and Fr. tuyauterie [lit. ‘pipes’] for “urinary system”). Underlying these semantic processes, the same structural metaphors in both languages were identified: VAGUER IS BETTER (widening), LESS OF FORM IS LESS OF CONTENT (reduction), and THE BODY IS A MACHINE/ORGANS ARE CONTAINERS (analogy). The examples show that these categories are not fully exclusive. Because lay terms used by patients during interview are a source of major misunderstandings on the part of healthcare professionals who are not native speakers of their patients’ language, pedagogical guidelines are provided so as to encourage Language for Medical Purposes (LMP) teachers to incorporate the study of patientese into their course. In my conclusion, I offer two hypotheses that both need further exploration: the probable evolution of patients’ terminology towards enhanced technicality under the influence of both medical TV series and the Internet, and consequently, the plausible use of technical terms as new euphemisms.