As for the word kava:
"In Polynesia, people also use the word kava and its cognates as adjectives to describe unpleasant flavors of foods and drinks. In the Cook Islands, for example, the word kavakava means “bitter” (Whistler 1990). In Hawai’i and the Marquesas, ‘ova signifies “bitter,” “sour,” “sharp,” and “pungent.” In Tahiti the range of meaning of ‘ova is broader, including “bitter,” “sour,” “acid,” “acrid,” and “pungent” (Churchill 1916b; Petard 1984). A similar semantic pattern occurs in Fiji, where kava is known as yaqona (pronounced yanggona). The word probably derives from *kona, meaning “bitter” (Crowley 1990). Early Polynesians probably borrowed both the plant and the semantic pattern of associating its use with sensations of bitterness, but replaced the Fijian word *kona with their own *kawa. Alternatively, the Fijians may have modified the-Polynesian word *kava or both the Fijians and the Polynesians may have adopted their kava nomenclature from a third source. One indication of antiquity of words is semantic opacity, so a transparency like the extension of a word for bad-tasting to name the beverage can be taken to indicate a comparatively recent act of naming. It might also be supposed that the Polynesian and Fijian terms for kava are younger than some of their linguistically opaque northern Melanesian counterparts. Green has suggested that the Polynesian word kava, like pottery drinking bowls and cups, dates back to the emergence of the Proto-Polynesian language approximately 2800 to 2500 years ago (personal communication, 1990).
If so, then kava’s subsequent northwestward movement along Lapita trade networks might explain scattered reflexes of Proto-Polynesian *kawa in the Admiralties, Micronesia, and mainland New Guinea (Brunton 1989). On Tongoa, for example, a cultivated form of P. wichmannii is called kau. On the island of Baluan in the Admiralties, kava (both P. wichmannii and P. methysticum) is also called kau. Along the Maclay Coast, south of Madang, kava is likewise called keu or kau. Similar linguistic forms exist on the two Micronesian islands where kava is (or was) consumed: on Pohnpei kava is known as sakau, and on Kosrae is called seka (Glassman 1950, 1952). Compared with the linguistic situation in Polynesia, that in Melanesia exhibits a far more complex and more diverse pattern of vernacular kava names. These names, along with practices of kava consumption and cultivation, are very localized. The diversity might be explained in part by the greater availability and suitability of land for kava cultivation on the larger Melanesian islands and by the more pronounced cultural diversity of this region. It might also be explained by the greater antiquity of kava drinking in Melanesia."
Lebot, Vincent; Merlin, Mark; Lindstrom, Lamont. Kava: The Pacific Elixir: The Definitive Guide to Its Ethnobotany, History, and Chemistry (Kindle Locations 526-530). Inner Traditions/Bear & Company. Kindle Edition.
