Sixteenth- and seventeenth-century chroniclers call attention to the Incas having had a 'particular language', used exclusively by members of the court. The sparse linguistic material attributed to it consists of barely a dozen proper names which 'El Inca' Garcilaso de la Vega, unable to explain through his Quechua mother tongue, assumed must belong to the purported secret language. On closer inspection most of these words do turn out to be explicable in terms of either a Quechua or an Aymara origin. Nevertheless, a small amount of extant onomastic material - mostly Inca institutional names - cannot be traced back to either, and points to a third language instead. This chapter makes the case that this could have been Puquina, once a major language of the Titicaca Basin, whence the mythical Incas set out on their journey to Cuzco. Linguistic, mythohistorical, and archaeological evidence are offered support of this hypothesis.