The Proto-Oceanic etymon *tabu has hardly been studied outside Polynesian, yet it is attested in other Oceanic languagesalbeit with different meanings. This study describes the polysemies observed for modern reflexes of *tabu, with an initial focus on Vanuatu. Sometimes, *tabu words simply refer to the mundane warning signs put up in various locations to fend off unwelcome visitors. But reflexes of *tabu are more often linked with supernatural powers, good or evil, and with the sense of awe and fear they induce upon us. The root may evoke the numinous power of high-ranked dignitaries; or the world of ancestral spirits and ghosts, and the forces of death. The diverse array of meanings attached to *tabu words is best synthesized in the form of a semantic map. This visual tool helps picture the internal organization of the root's polysemy, and can be used as a background as we compare modern languages with each other. By applying principles of the Comparative method, we can reconstruct the meaning of *tabu at the level of Proto-Oceanic: 'forbidden, off limits; sacred, due to a sentiment of awe before spiritual forces'. Finally, semantic maps reveal their full potential as we take a dynamic perspective, and retrace the evolution of *tabu from its original meanings to the various polysemies it has acquired in modern languages.