The deportation of the Acadians from Nova Scotia by the British in 1755-1763, which decimated more than half the Acadian population and destroyed their community, is largely unknown in the global public sphere. In this dissertation, I explain this ignorance. Unlike previous scholars who treat the Acadian tragedy as a case of ethnic cleansing, I argue that the concept of genocide provides a narrative structure according to a target, a possible “intent,” acts, and memory, which enables us to see the unidentified pattern of Acadian exclusion in history: cultural unthinkability. As early 17th century French settlers became Acadians through intermarriages with the Mi’kmaq, their Indigenous neighbors, they became neutrals in imperial conflicts. Considering this context, I show how European policies of settler colonialism lacked categories to grasp the cultural roots of Acadian neutrality, made Acadians a target as an unthinkable group, and resulted in a genocidal plan and acts that precluded authorities from representing Acadians coherently in Enlightenment racial discourse. I then unveil the role of Acadian memory in the creation of the term genocide, a story ignored by the literature, given the lasting Acadian inability to fit into identity norms. My argument opens up a reconsideration of how human societies produce otherness. Unlike Edward Said in Orientalism (1978), I illuminate a distinction between the other for whom a standard identity category is constructed, however biased or false, and the other for whom no official category is made, such as the unthinkable Acadian, largely erased from most historical narratives.