[SE cassava, ‘A plant, called also by its Brazilian name Manioc [...] two varieties (or species) of which are extensively cultivated in the West Indies and tropical America, as also in Africa, for their fleshy tuberous roots, which yield the greatest portion of the daily food of the natives of tropical America’ (OED)]
(US) the head.
B. SchulbergOn the Waterfront (1964) 192: What was he doing — getting soft in the casaba.