Because pineapple is the fruit of a creature called Ananas comosus. This is its (universal) scientific name. Describing this plant as a mix of a pine and an ap

Because pineapple is the fruit of a creature called Ananas comosus. This is its (universal) scientific name. Describing this plant as a mix of a pine and an apple is a particularly poor choice having in mind that this is a monocot, thus neither directly related with coniferes nor with dicots. When we have yet a word that is unique, short and exclusive for a new type of organism, and everybody is familiar yet with the fruit and its peculiar flavor, adopting that word would be wise. In the same way as calling a type of animal "Sengis" should be preferred over the old and more verbose "elephant-shrews". Specially after we discovered that they aren't related with shrews at all, and totally deserve its own unique name. Of course tradition stands in the way, so I'm just digressing