The story of tilapia

Just last week, a friend and I went to dinner. He ordered tilapia. I asked him what that was. All he knew was that it was fish so I claimed that "tilapia" was in fact the Spanish word for plankton. Brows furrowed. Worried silence ensued. He was pretty sure I was joking but neither of us could be sure I was wrong. Now we know I was both kidding and wrong.