Nomenclature
The name given to the plant in Guaraní, language of the indigenous people who first cultivated and enjoyed mate, is ka'a, which has the same meaning as "herb". Congonha, in Portuguese, is derived from the Tupi expression, meaning something like "what keeps us alive", but a term rarely used nowadays. Mate is from the Quechua mati, meaning "gourd" or the cup made from a gourd. The word Mate is used in both, Portuguese and Spanish languages.
The pronunciation of yerba mate in Spanish is . The accent on the word is on the first syllable, not the second as might be implied by the variant spelling "maté". The word hierba is Spanish for "herb"; yerba is a variant spelling of it which was quite common in Argentina. (Nowadays in Argentina "yerba" refers exclusively to the "yerba mate" plant) Yerba mate, therefore, originally translated literally as the "gourd herb", i.e. the herb one drinks from a gourd.
The (Brazilian) Portuguese name is either erva-mate (also pronounced or in some regions), the most used term, or rarely "congonha", from Old Tupi kõ'gõi, which means "what sustains the being". It is also used to prepare the drinks chimarrão (hot), tereré (cold) or chá mate (hot or cold). While the chá mate (tea) is made with the toasted leaves, the other drinks are made with green leaves, and are very popular in the south of the country. Most people colloquially address both the plant and the beverage simply by the word mate.
Both the spellings "mate" and "maté" are used in English, but the latter spelling is never used in Spanish where it means "I killed" as opposed to "gourd". There is no variation of spellings in Spanish. The addition of the acute accent over the final "e" was likely added as a hypercorrection, indicating that the word and its pronunciation are distinct from the common English word "mate".
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