Sex differentiable terms are lexemes that distinguish sex or gender among both humans and nonhuman animals. Focused linguistically and ethnographically on the island of Flores and neighboring islands in eastern Indonesia, the main topic is sex differentiable terms for animals and how these form distinct patterns in different languages. A pattern whereby nonhuman animals are sexually distinguished mainly by two pairs of terms is identified both for the Ngadha-Lio languages of central Flores and for Lamaholot, spoken in the extreme eastern parts of the island and on neighboring islands to the east. Different patterns are found in Sikkanese (spoken in the region intervening between central Flores and Lamaholot), among Manggarai-speakers in western Flores, and on the island of Sumba. In varying degrees, these correspond to the system of sex differentiables employed in Western Malayo-Polynesian languages like Javanese and Malay. Concerning Central Malayo-Polynesian languages spoken within one part of eastern Indonesia, this comparative study contributes to a discussion of a possible original Malayo-Polynesian pattern of sex differentiable classification and a consideration of how central and eastern Florenese patterns may have developed.