title_body: How to link extraterrestrial animal names from other language with terrestrial languages? As title states; how to name extraterrestrial fauna/flora to human languages, would reffering to animals similar to cows as to cows and to plant that bears round red fruits as to apple be linguisticly acceptable? Or maybe new words would have to be put in place to describe those creatures?
upvoted_answer: I think, the more generic a term is, the better you can use a known term in your native language. The more specific a term is, the greater is the need for some circumlocution or some conlang term.
  
  Examples: Specific kinds of flowers and trees in Tolkien's "Lord of the Rings" have constructed names like mallorn, niphedril, or simbelmyne. He consistently used pipe-weed (the word tobacco is used by the narrator, but not in dialogues). Already on the level of genera, Tolkien uses terms like pine tree, oak, ... and of course there is grass, there are trees, there are horses and so on.
  
  Whether you want to call some space creatures "cows" depends on the picture the word "cow" evokes and the uses of cows (Do they give milk and flesh? Can you use oxen for ploughing or driving a cart?) in your fictional culture.