Фасмер:
Слово:ананас,
Ближайшая этимология: из нем. Ananas или франц. ananas, которое происходит через порт. ananas из тупи (Бразилия).

Из Википедии отсюда:
Among the many Tupi loanwords in Portuguese, the following are noteworthy for their widespread use:
* abacaxi (pineapple, literally: "perfumed fruit")
Словарь португальского:
ananás - do Tupi-Guar. Naná
И еще дополнение отсюда:
From South America came batata "potato", from Taino; ananás and abacaxi, from Tupi-Guarani naná and Tupi ibá cati, respectively (two species of pineapple)...

Английский:
pineapple - used before 1350 to mean "pine cone;" the reference to the fruit of the tropical plant (from resemblance of shape) is first recorded 1660s, and pine cone emerged 1695 to replace pineapple in its original sense. For "pine cone," O.E. also used pinhnyte "pine nut."

И как это будет на разных языках (в основном, кстати, как раз ananas!):
http://www.proz.com/forum/linguistics/57978-do_you_have_2_words_for_the_word_fruit_pineapple_in_your_language.html