This chapter considers questions of terminology used in the discussion and presentation of models of cognition in twelfth-century Western European philosophy and medical theory, both in attempts to translate technical terms that describe human cognitive and intellective functions between languages, from Greek or Arabic into Latin, and within the same Latin language. The case study is the word ingenium, often translated into modern English as “wit” or “ingenuity,” a kind of power or function that leads to the discovery of new things. For Alfanus and Burgundius of Pisa, translators of Nemesius’s De natura hominis, and for natural philosophers such as Adelard of Bath and William of Conches, finding the language to talk about thought means reckoning with the uncertainty and slippage of translation. Such uncertainty brings into a starker focus the difficulty in finding terms—in any language—that adequately convey the experience of thought, so that attention to language allows a sharper understanding of the problems in describing cognition and a greater awareness of how theories of the mind emerge, change, or decline.