A scientific nomenclature of erotic age preferences informed the mid- through late nineteenth century joint appearance of homosexuality and sexual abuse of minors on the medico-legal scene. Yet, even in the twenty-first century, legal, psychiatric and culture-critical dimensions of related terms are rarely cleanly distinguished. Review of primary sources shows the ongoing Western suspension of notions of ‘sick desire’, alongside and beyond the medicalisation of homosexuality, between metaphor, legal interdiction and postulated psychopathology. Virtually all early attention to erotic age preference occurred in the context of emergent attention to erotic gender preference. Age of attraction and age difference centrally animate modern homosexuality’s pre-modern past; its earliest psychiatric nomenclature and typologies (1844–69); its early aetiologies stipulating degrees of sexual differentiation (1890s); its concomitant sub-classification (1896–1914); its earliest psychophysiological tests (1950s); and, finally, its post-psychiatric, social scientific typologies (1980s). Several identifications of ‘paedophilia’ were seen throughout the 1890s but as a trope it gained cultural momentum only during, and as a seemingly intriguing corollary of, the progressive depsychiatricisation of homosexuality across the Anglo-European world (late 1950s through 1980s). Early twentieth century sources varied in having it denote (1) a distinct perversion, thus possible ‘complication’ of sexual inversion (2) a discrete corollary of psychosexual differentiation akin to gender preference (3) a distinct subtype of fetishism, thus a likely imprint of early seduction (4) a more intricate expression of erotic symbolism or psychosexual complex or (5) a taste answering to culture, a lack of it, or a libertine disregard for it.